“Docket No. 80-2848 SECRETARY OF LABOR, Complainant, v. COLLIER-KEYWORTH COMPANY, Respondent.OSHRC Docket No. 80-2848ORDER OF REMANDOn April 6, 1987, the Commission issued a decisionholding that Table G-16 of the occupational noise standard at 29 C.F.R. ? 1910.95(a)-(b)did not cover impulse noise. The Commission based its holding on the language of thestandard, its legislative history and the Secretary’s interpretation of the standardshortly after its adoption. In weighing the legislative history of the standard and theSecretary’s interpretation of the standard shortly after its adoption, we referred todocuments that we officially noticed under section 7(d) of the Administrative ProcedureAct, 5 U.S.C. ? 556(e). We also stated that we would afford the Secretary the opportunityto rebut the officially-noticed documents with documents and other evidence of his intentwhen he adopted the standard in 1969. The Commission therefore ordered that certaincitation items be vacated unless the Secretary requested an opportunity within 15 days torebut officially-noticed documents.The Secretary has filed a motion for an extension oftime to gather, review and possibly submit documents relevant to the intent of thestandard’s drafters with respect to the coverage of impulse noise. The Secretary asks forextension of three weeks, through May 11, 1987. Ordinarily, we would simply grant thismotion, for it is supported by good cause. In this case, however, the Secretary’s motionwould, if granted, cause the period of time to extend beyond the term of one of theCommission’s two current members. The Commission might for some time therefore be unableto directly act on further motions in the case and might be unable to remand the matter tothe administrative law judge to receive further documents and supporting testimony.Inasmuch as this issue is an important one and should be expeditiously resolved, we willgrant the motion and remand this case to the administrative law judge now withinstructions to afford the Secretary an opportunity to rebut officially-noticed documentswith evidence of the Secretary’s intent when he adopted the standard in 1969. The judgeshall expeditiously prepare a supplemental decision affirming, modifying or vacating thosecitation items relevant to the impulse noise issue in light of any additional evidencethat the parties submit. If the Secretary does not desire that the record be re-opened,the judge shall issue a decision vacating the citation items in accordance with ourdecision of April 6, 1987.Accordingly, this case is remanded to theadministrative law judge for further proceedings.FOR THE COMMISSIONRay H. Darling, Jr.Executive SecretaryDATED: April 22, 1987SECRETARY OF LABOR, Complainant, v. COLLIER-KEYWORTH COMPANY, Respondent.OSHRC Docket No. 80-2848DECISIONBefore: BUCKLEY, Chairman; WALL, Commissioner.BY THE COMMISSION:This case is before the Occupational Safety andHealth Review Commission under 29 U.S.C. ? 661(j), section 12(j) of the OccupationalSafety and Health Act of 1970, 29 U.S.C. ?? 651-678 (\”the Act\” or \”theOSH Act\”). The Commission is in adjudicatory agency, independent of the Department ofLabor and the Occupational Safety and Health Administration (\”OSHA\”). It wasestablished to resolve disputes arising out of enforcement actions brought by theSecretary of Labor under the Act and has no regulatory functions. See section 10(c)of the Act, 29 U.S.C. ? 659(c).I. IntroductionCollier-Keyworth Company manufacturers swivel andtilt mechanisms for office chairs in a plant in Gardner, Massachusetts. In April 1980,OSHA industrial hygienists inspected Collier-Keyworth’s plant to determine whether thecompany was in compliance with the occupational noise standard at 29 C.F.R. ? 1910.95(a)-(b). From measurements made during the inspection, OSHA concluded that employees whooperated power presses and lathes at the plant were exposed to noise in excess of thelimits established by the standard. It therefore cited Collier-Keyworth for variousviolations of section 1910.95. At the time of the alleged violations, the standardprovided:[[1]]? 1910.95 Occupational noise exposure.(a) Protection against the effects of noise exposureshall be provided when the sound levels exceed those shown in Table G-16 when measured onthe A scale of a standard sound level meter at slow response. . . .*\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0*\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0*(b)(1) When employees are subjected to sound exceeding those listed in Table G-16,feasible administrative or engineering controls shall be utilized. If such controls failto reduce sound levels within the levels of Table G-16, personal protective equipmentshall be provided and used to reduce sound levels within the levels of the table.\u00a0\u00a0\u00a0 (2) If the variations in noise level involve maxima at intervalsof 1 second or less, it is to be considered continuous.\u00a0\u00a0\u00a0 (3) In all cases where the sound levels exceed the values shownherein, a continuing, effective hearing conservation program shall be administered.Table G-16–Permissible Noise Exposures[[1]]Duration per day, hours\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0Sound level dBA slow response8……………………………………………………………………………90 6……………………………………………………………………………92 4……………………………………………………………………………95 3……………………………………………………………………………97 2…………………………………………………………………………..100 1? ………………………………………………………………………..1021……………………………………………………………………………105?…………………………………………………………………………..110? or less ………………………………………………………………..115[[1]] When the daily noise exposure is composed of two or more periods of noise exposureof different levels, their combined effect should be considered, rather than theindividual effect of each. If the sum of the following fractions: C1\/T1+C2\/T2 [+ . . .] Cn\/Tn exceeds unity, then,the mixed exposure should be considered to exceed the limit value. Cn indicatesthe total time of exposure at a specified noise level, and Tn indicates thetotal time of exposure permitted at that level.Exposure to impulsive or impact noise should not exceed 140 dB peak sound pressurelevel.The principal dispute in this case is whether TableG-16 regulates a kind of noise called \”impulse noise.\” The dispute arises inthis case because, in determining whether Collier- Keyworth’s employees were exposed tomore noise than Table G-16 permits, OSHA employed measuring devices–sound level metersand personal noise dosimeters–that registered impulse noises in Collier-Keyworth’s plant.Collier-Keyworth argues that Table G-16 was not intended to regulate impulse noise andtherefore that OSHA’s measurements were unreliable.A. Measuring Noise Exposure Under Table G-16Before we set out and discuss these arguments, weshall discuss generally the two methods of proving that an employer has violated thelimits for noise exposure in Table G-16 of section 1910.95(a)-(b). First, the Secretarymay show that an employee is subjected to a sound level equal to or greater than a levellisted in Table G-16 for a longer period of time than the table permits. For example, theSecretary could meet his burden of proof by showing that an employee is exposed to 92 dBAor higher for more than six hours, or to 105 dBA higher for more than one hour. If thismethod is used, however, sound levels that last for less than their permissible periodswould have to be disregarded. Yet, sound levels in industrial plants often fluctuate andcontinue for less than their permissible periods; some last for only a few minutes orseconds. This method therefore can result in a substantial underestimate of an employee’stotal noise exposure.[[2]]The second way in which the Secretary can showoverexposure overcomes this difficulty but introduces others. The second method uses thecumulation formula in the footnote to Table G-16. This formula explains how one maycalculate an employee’s noise dosage when sound levels vary throughout the workday. Underthe cumulation formula, a fraction, Cn\/Tn (Cn being thetime the employee is exposed to that level and Tn being the exposure time permitted atthat level), is calculated for each different noise level to which an employee is exposedduring the workday. At the end of the day, all the fractions thus calculated are addedtogether. If the total is more than one (\”unity\”), the employee has been exposedto noise exceeding permitted limits.The cumulation formula yields a more accuratedetermination of an employee’s total noise exposure, for it counts as part of theemployee’s noise exposure sound levels that continued for less than the permissibleperiod. This permits each variation in noise level to be given its proper weight and to becumulated. However, the cumulation formula is considerably more difficult to apply. AnOSHA compliance officer must hold the microphone of a sound level meter in an employee’shearing zone; read each different sound level registered on the meter; with a watch,determine the duration of that level; and record on a notepad each sound level and itsduration. Where the noise level is constantly varying, however, it is extremely difficultto manually make the many measurements and calculations necessary to apply the formula.And, because the task is so difficult to perform accurately, compliance officers cannotsurvey the exposure of more than a few employees in a day.To overcome these problems, the personal noisedosimeter was developed. The dosimeter is an electronic instrument that contains thecircuitry of a standard sound level meter along with other circuitry. A dosimeter is smallenough to be worn by an employee throughout the workway as he goes about his duties. Thedosimeter microphone, which is part of the dosimeter’s sound level meter, is placed in theemployee’s hearing zone, where it continually detects the noise to which the employee issubjected. The sound level meter circuitry within the dosimeter measures the varying soundlevels and sends that information to the other dosimeter circuitry, which automaticallycalculates and sums the fractions as required by the cumulation formula.[[3]] At the endof the workday, the dosimeter gives a reading in terms of the percentage of the permitteddaily dosage. A dosimeter reading of 100 percent means that the sum of the fractions isone. A dosimeter reading exceeding 100 percent thus means that the permitted amount ofnoise dosage has been exceeded. See New England Container Co., 84 OSAHRC55\/A2, 12 BNA OSHC 1368, 1371\u00a0 n. 7, 1984-85 CCH OSHD ? 27,148, pp. 35,045-46 n. 7(No. 78-1539, 1984).The Secretary measured the noise exposure ofCollier-Keyworth’s employees using dosimeters. Because the dosimeters indicated thatCollier-Keyworth’s power press and lathe operators were exposed to more than 100 percentof the permitted daily dosage, the Secretary alleges that the employees were exposed tonoise exceeding the limits permitted by the standard. Collier-Keyworth contends that thedosimeter readings cannot be relied upon to find overexposure. The company raises a numberof potential inaccuracies with dosimeters, but its principal argument is that thedosimeter readings obtained by the Secretary were unreliable because some of the noisethey measured was impulse noise, a type of noise the company argues is not intended to beincluded in dosage calculations under Table G-16.B. Impulse NoiseImpulse noise is noise of brief duration produced bya short-lived physical phenomenon, such as a gunshot, a clap of thunder, or a power pressstroke. When such noise arises from the impact of two objects, it is called impact noise.The distinction between impact noise and other impulse noise is not important to theissues before us. A provision of the standard, however, requires that we distinguishbetween impulse noises based on the time between their peaks or maxima. Subsection1910.95(b)(2) states that \”[i]f the variations in noise level involve maxima atintervals of 1 second or less, it is to be considered continuous.\” This provisionreflects that much industrial noise consists of series of repetitive impulses and that theimpulses are often spaced so closely together as to sound continuous. One witness gave theexample of a gearbox, in which noise originates as the impact of gear teeth on gear teethbut the impacts occur so frequently that the ear does not hear the individual impacts.Subsection (b)(2) provides a criterion for classifying closely-spaced impulse noise ascontinuous noise. Concomitantly, expert witnesses for both parties testified that noise isconsidered to be \”impulse noise\” if it involves maxima that are less than onesecond in duration and more than one second apart.Collier-Keyworth’s arguments focus both on the wordsof the standard and its background. Collier-Keyworth points to a provision that is nowprinted as the second paragraph of the footnote to Table G-16. That provision states that\”[e]xposure to impulsive or impact noise should not exceed 140 dB peak sound pressurelevel.\” Collier-Keyworth argues that his provision demonstrates that the standardtreats impulse noise differently from other noise. It also points to subsection (b)(2) ofthe standard. Because the one-second interval mentions in that subsection corresponds tothe interval that is universally recognized as the dividing line between impulse noise andcontinuous noise, the company contends that this represents the standard’s intent to drawa line between impulse noise and continuous noise, with the latter regulates by Table G-16calculation and the former excluded. It also relies on various documents and testimony tosupport its argument that, when the noise standard was adopted, the Secretary did notintend to regulate impulse under Table G-16.Administrative Law Judge Foster Furcolo agreed withCollier-Keyworth’s argument that Table G-16 was not intended to cover impulse noise. Onthat basis, the judge vacated the citations in their entirety. We agree with the judge’sconclusion that impulse noise must be excluded when determining whether Table G-16 limitshave been exceeded. We further find that the employees covered by items 1a(B) and (D), and1b(B) and (D), of the citation were exposed to considerable amounts of impulse noise, andas to those employees the Secretary did not prove overexposure to continuous noise.Employees covered by citation items 1a(A) and (C), and 1b(A) and (C), however, wereexposed to noise defined as continuous by subsection (b)(2) of the standard, i.e., tonoise with impulses occurring more frequently than once per second. Although we find thatthe Secretary proved that those employees were exposed to noise exceeding permittedlimits, we also find that the Secretary did not show that Collier-Keyworth failed to takethe steps required by the standard to protect the employees. We therefore affirm thejudge’s disposition vacating all citation items.II. Does Table G-16 Cover Impulse Noise?The record establishes, as we shall discuss morefully later, that at least some of the noise measured during OSHA’s inspection ofCollier-Keyworth’s plant was impulse noise, that is, noise with sharp energy peaks lastingless than one second and spaced more than one second apart. If Table G-16 does notregulate impulse noise–or, stated differently, if impulse noise must be excluded from thecalculation of dosage when one uses the cumulation formula in Table G-16–then dosimeterreadings that include impulse noises produce readings that are too high. Therefore, indetermining whether the readings obtained by OSHA show that Collier-Keyworth’s employeeswere exposed to excessive noise, we must first address Collier-Keyworth’s argument thatsection 1910.95(a)-(b) does not intend for impulse noise to be included in dosagecalculations employing Table G-16 limits.[[4]]A. The Scope of Our InquiryThe Secretary contends that Collier-Keyworth’sargument should be rejected because the record compiled in this litigation \”containssubstantial expert testimony that impulsive…noise is no less damaging to hearing thencontinuous noise.\” The Secretary cites the testimony of several witnesses, includingthat of a physician specializing in otolaryngology, and argues that the degree ofpermanent hearing loss is directly proportional to the amount of acoustic energytransferred to the ear.[[5]] The Secretary reasons that because the energy associated withprolonged exposure to impulse noise can cause irreversible hearing loss, it should beregulated by Table G-16.We do not dispute that there is now reason to believethat impulse noise can cause hearing loss. But in the absence of an OSHA standard, we donot have the authority to regulate exposure to impulse noise. New medical and scientificevidence is not relevant if, as Collier- Keyworth claims, the Secretary did not intendTable G-16 to cover impulse noise when he adopted it. As an adjudicative body, theCommission must take the standard as it finds it and apply the standard in accordance withthe Secretary’s intent at the time of promulgation. See Oscar Mayer & Co. v.Evan, 441 U.S. 750, 758 (1979) (intent of Congress that enacted statute iscontrolling). The Commission has no authority to \”update\” any standard throughinterpretation according to the latest scientific findings. Such legislative authorityresides in the Secretary, who, in rulemaking, may consider whether new findings physicalagents make regulation necessary and what new duties should therefore be imposed onemployers. For the Commission to interpret a standard to produce what it believes will begreater protection for employees than the Secretary originally intended both usurps theSecretary’s rulemaking authority and detracts from the statutory right of those affectedby a rule to participate in the rulemaking process.B. The Language of Section 1910.95(a)-(b)The Secretary argues that the plain language of thestandard indicates that he intended to regulate impulse noise under Table G-16. He notesthat section 1910.95(a) requires protection whenever \”sound levels\” exceed TableG-16 values, and argues that the all-inclusive phrase \”sound levels\” draws nodistinction between impulse noise and non-impulse noise.Standard must, however, be read as a coherent whole,and Collier-Keyworth points to two provisions it contends indicate an intent to excludeimpulse noise from Table G-16.Collier-Keyworth points to the statement, now printedas the second paragraph of the footnote to Table G-16, stating that exposure to peak soundpressure levels of impulse noise should be limited to 140 dB. It argues that this specialprovision for impulse noise shows an intent to treat impulse noise differently from othernoise. The Secretary, on the other hand, contends that this provision demonstrates thatwhere the standard intended to distinguish impulse noise from other noise, it did soexplicitly.We think that there is force in Collier-Keyworth’sargument. Although Table G-16 sets a ceiling of 115 dBA on sound pressure levelsregardless of the duration of exposure, Wheeling-Pittsburgh Steel Corp., 83 OSAHRC16\/A2, 11 BNA OSHC 1292, 1294, 1983-84 CCH OSHD ? 26,482, p. 33,673 (No. 15647, 1983),the special provision for impulse noise warns against impulse noise that exceeds 140 dB.This provision would be superfluous if, as the Secretary argues, the all-inclusive phrase\”sound levels\” in section 1910.95(a) means that all sound, both impulse andnon-impulse, must stay within the limits in Table G-16. Thus, the impulse noise provisionsuggests that the \”sound levels\” regulated by Table G-16 do not include allsound levels and that impulse noise must be excluded from calculations under TableG-16.[[6]]It might seem somewhat odd that an answer to thisimportant question might be suggested by a brief second paragraph of a footnote to atable. However, the drafters of the standard did not intend the impulse noise provision tobe relegated to such an obscure position. The provision was originally placed in the textof the standard but later became located in the footnote as the result of a printer’serror.[[7]] We therefore ascribe no importance to the placement of the impulse noiseprovision.The second provision on which Collier-Keyworth reliesis subsection (b)(2), which defines noise as continuous if the peaks are closer than onesecond apart. Collier-Keyworth contends that the Secretary’s classification ofclosely-spaced impulses as continuous noise must be viewed as evidence of an intent todistinguish impulse noise from continuous noise and to exclude impulse noise from thecriteria established for continuous noise. The Secretary’s brief does not addresssubsection (b)(2) or suggest how it could be reconciled with his position that impulsenoise is subject to the limits of Table G-16.We agree with Collier-Keyworth that subsection (b)(2)appears to represent an attempt to distinguish impulse noise from continuous noise. Bothparties agree that continuous noise, i.e., noise of constant intensity, is included inTable G-16 calculations. By defining noise with peaks closer than one second apart ascontinuous, subsection(b)(2) obviously means that such noise is to be included in dosagecalculations. A provision that says something is included, however, implies that somethingelse is excluded, for there would otherwise be no reason for the provision. As theone-second criterion in subsection (b)(2) represents the distinction between impulse noiseand non-impulse noise, the section suggests that the drafters of the standard intended toexclude impulse noise from Table G-16.On balance, both the 140 dB peak limit for impulsenoise and subsection (b)(2) suggest that impulse noise is excluded from dosagecalculations under Table G-16. Nevertheless, the standard is not entirely clear on itsface. It does not expressly exclude impulse noise from Table G-16. As the Secretary pointsout, the standard uses the broad term \”sound levels.\” In light of the ambiguity,we look to evidence extrinsic to the standard to determine whether the drafters intendedto exclude impulse noise from such calculations.C. Legislative History of the StandardSection 1910.95 is derived from 41 C.F.R. ?50-204.10, a standard that was originally promulgated in 1969 by the Labor Department’sBureau of Labor Standards to regulate work by government contractors under theWalsh-Healey Government Contracts Act, 41 U.S.C. ?? 35-45. Section 1910.99 (listingsources of standards); see generally American Can Co., 82 OSAHRC5\/A2, 10 BNA OSHC 1305, 1306-1308, 1982 CCH OSHD ? 25,899, pp. 32,409-11 (No. 76-5162,1982) (setting out course of promulgation of standard). Because 41 C.F.R. ? 50.204.10qualified as an \”established federal standard\” under section 3(10) of theOccupational Safety and Health Act of 1970 (\”the OSH Act\”), the Secretary ofLabor was authorized to adopt it as an OSHA standard without further rulemakingproceedings. Section 6(a) of the OSH Act, 29 U.S.C. ? 655(a). The Secretary did so on May29, 1971, adopting 41 C.F.R. ? 50-204.10 verbatim as an OSHA standard and codifying it at29 C.F.R. ? 1910.95. 36 Fed. Reg. 10466, 10518. Because the Secretary did not, and–withexceptions not pertinent here–could not substantively amend the standard when hesummarily adopted it as an OSHA standard, we must give the standard the same meaning ithad under the Walsh-Healey Act. See American Can, 10 BNA OSHC at 1310-11,1982 CCH OSHD at pp. 32,413-14; Sherwin-Williams Co., 84 OSAHRC 28\/A2, 11 BNA OSHC2105, 2109-10, 1984-85 CCH OSHD ? 26,986, pp. 34,701-02 (No. 14131, 1984).The promulgation of 41 C.F.R. ? 50-204.10represented the culmination of a long effort by the effort by the Labor Department andother organizations to develop exposure limits for noise that would protect workersagainst noise-induced hearing loss. Although the preamble that accompanied the standardwhen it was adopted under Walsh-Healey Act sheds no light on the light on the impulsenoise question, the record in this case contains evidence of events leading up theadoption of the Walsh-Healey standard, as well as evidence of the Secretary’sinterpretation of the standard shortly after its promulgation. The parties presentedwitnesses, James H. Botsford and Herbert H. Jones, who were personally familiar with manyof the events leading up to the standard’s adoption. Their testimony is supplemented bydocumentary exhibits introduced by the parties and other documents that we officiallynotice under section 7(d) of the Administrative Procedure Act, 5 U.S.C. ? 556(e).[[8]]Our examination of the record and the material that we officially notice, together withthe words of the standard, lead us to conclude that the Secretary did not intend for TableG-16 to regulate impulse noise when the standard was promulgated.The documents we officially notice include only LaborDepartment publications and scientific papers cited in documents that were introduced intoevidence. Our purpose in taking official notice is not to determine whether impulse noiseis harmful or whether the preponderance of scientific thinking in 1969 would have favoredthe regulation of impulse noise under Table G-16. As we have said, weighing such evidenceis not our function but the Secretary’s. Our purpose is instead to determine the intent ofthe Secretary in 1969 by examining the body of knowledge on impulse noise that influencedthe adoption of the standard. Because our decision rests in part on these officially-noteddocuments, we shall afford the Secretary an opportunity to rebut them with documents andother evidence of his intent when he adopted the standard.In 1960, the Walsh-Healey standard for noise statedin its entirety: \”Noise shall be reasonably reduced or eliminated as a means ofpreventing fatigue or accident.\” 25 Fed. Reg. 13809, 13825 (1960). In early 1964, thedepartment proposed numerical guidelines that would establish weekly exposure limits for\”continuous steady noise\” and also establish a peak limit of 135 dB for\”any exposure…however short in duration other than impact noises….\” U.S.Dept. of Labor, Bureau of Labor Standards, \”Suggested Language for a Noise ControlProgram,\” as printed in \”Noise: Guidelines for control issued by Bureauof Labor Standards,\” Safety Standards 18, 20-21, 24 (U.S. Dep’t of Labor,March-April 1964); see also U.S. Dept. of Labor, Bureau of Labor Standards, SuggestedLanguage for a Noise Control Program (1965).The Technical Committee on Noise of the AmericanIndustrial Hygiene Association (\”AIHA\”) met in May 1964 with Jones (then of theU.S. Department of Health, Education and Welfare) and Botsford (then employed by BethlehemSteel and its senior noise control engineer). The committee members believed that thenewly-published guidelines had technical errors in them and that better guidelines couldbe developed. The AIHA therefore decided to offer to the Labor Department the formation ofa committee of noise experts to recommend different guidelines. The Labor Departmentagreed to the formation of such a committee, which was called the Inter-Society Committeeon the Guidelines for Noise Exposure Control (\”Inter-Society Committee\”). Thecommittee consisted of two members from each of five technical societies: the AIHA, theAmerican Conference of Governmental Industrial Hygienists (\”ACGIH\”), theAmerican Academy of Ophthalmology and Otolaryngology, the American Academy of OccupationalMedicine, and the Industrial Medical Association. One of the ACGIH representatives was Dr.Floyd Van Atta of the Labor Department, who, according to Jones, \”had primaryresponsibility in the noise area as far as the Department of Labor was concerned.\”The Inter-Society Committee issued a report in 1967,which it characterized as the \”first attempt to extract and condense pertinent datafrom various scientific literature into a meaningful and authoritative guide.\”Inter-Society Committee, \”Guidelines for Noise Exposure Control,\” 28 Am. Indus.Hygiene J. 418, 419-22 (Sept.-Oct. 1967)(I-S). For this inquiry, it is noteworthy that thecommittee’s guidelines were directed at developing exposure criteria for only\”steady\” noise.[[9]] The following are excerpts from the guidelines:I. Forward*\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0*\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0*Noise-induced hearing loss increases with both the intensity of the noise and theduration of exposure. Generally, many years of exposure to high noise levels are requiredto produce significant permanent impairment in the exposed group; however, there will bemarked differences in the hearing of individuals and in their response to noise…These Guidelineswill be directed toward the prevention of that portion of the permanent hearing lossresulting from exposure to steady noise.*\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0*\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0*III. Occupational Hearing Loss Control Program*\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0*\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0*A. Evaluation of the Noise Hazard*\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0*\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0*1. Noise Measurement.Continuous or intermittent steady noise is readily measured by standard instruments;impulsive noise requires special procedures not considered here. [Footnote omitted.]*\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0*\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0*2. Hazard Rating.(a) Continuous Exposure. . . . The first two columns of Table 1 [omitted] indicatethe steady noise levels to which the various groups [of persons with hearing loss] wereexposed. . . .(b) Intermittent and Part-time Exposure. The studies on which Table 1 and Figure 1[omitted] are based, dealt with men exposed to noise during a normal workday, of eighthours’ duration. . . .The report went on to explain that, although therewere no long-term studies of the effects of intermittent exposures, the results of somestudies implied the \”simple rule\” that for each halving of daily exposure time, the noise levels may be increased by 5db up to a maximum of 115 dB . . . without increasing the hazard of hearing impairment.The application of this rule is illustrated in thefollowing table:Permissible Increase in db for less than Eight HoursExposure Daily Exposure Time (Hours) Permissible Increase Above Eight-Hour Criterion (Decibels) 8 0 4 5 2 10 1 15 ? 20 ? 25 Notably, the Inter-Society Committee’s report did notpropose any particular permissible exposure level; for this reason, the AIHA Board foundthe report unacceptable and suggested that the Inter-Society Committee be disbanded.Shortly thereafter, the ACGIH established its own committee to develop a permissibleexposure limit for noise as well as other physical agents. Jones was chairman of thiscommittee. The ACGIH Committee drafted a proposed standard that was published for publiccomment and accompanied by an explanatory article written by Jones, \”ACGIH’s ProposedThreshold Limit Value for Noise,\” 29 Am. Indus. Hygiene J. 537-40 (Nov.-Dec. 1968) (ACGIH).See generally Appendix A.1 to this decision.The most noteworthy aspect of the ACGIH Committee’sproposal is that it twice stated that its proposed limits would \”not apply to impulseor impact type of noise.\” ACGIH at 540 (proposed standard). Instead, theproposed standard stated, \”[i]t is recommended that exposure to this type of noiseshould not exceed 140 db peak sound pressure level.\” Id. Jones’ articleexplained the ACGIH Committee’s reasons for distinguishing between continuous noise andimpulse noise:After considering [various data], the Committeedecided that at the present time it appears desirable to establish a limit of 92 dBA for 4to 8 hours of exposure per day to broad band continuous noise. . . .Laboratory data. . .and. . .field data indicate that, when exposure is for less thana full 8-hour period or is intermittent in nature, the ear can tolerate more acousticalenergy per day than for a single exposure to continuous noise. Considering these twofactors, the limit is increased 5 decibels for each halving of exposure periods for thework day regardless of whether this is a single exposure or an exposure which isintermittent in nature.*\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0*\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0*Very little data is available upon which to base exposure to impact or impulsivenoise. It is known that exposure to a small number of 140 dB impulsive noises of shortduration will produce a temporary threshold shift. Until additional data is available, alimit of 140 dB is being set impact or impulsive noise.ACGIH at 538 (article) (references omitted).Thus, the criteria proposed by both the Inter-SocietyCommittee and the ACGIH Committee excluded impulse noise, with the exception of the ACGIHproposal for a peak limit of 140 dB for impulse noise. The reason they otherwise excludedimpulse noise was apparently because, as stated in Jones’ article, \”[v]ery littledata is available upon which to base exposure to impact or impulsive noise.\” Both theInter-Society Committee and the ACGIH Committee had cited a number of scientific studiescompleted by the late 1960’s attempted to measure the effect of noise on human hearing.These studies, which are excerpted in the appendix to this decision, had measured hearingloss caused by various degrees of noise exposure. Because most of them involved purelysteady-state noise, they formed a substantial body of evidence from which permissibleexposure limits and an exchange rate–the number of decibels by which sound levels couldrise if exposure time was halved–could be derived. However, there was considerably lessevidence on which to base permissible exposure limits for impulse noise. The scientistswho attempted to develop hearing protection criteria cautioned against applying themimpulse noise, and tended to regard impulse noise and continuous noise as two distinctproblems. The studies cited by the Inter-Society Committee and the ACGIH Committee dealingwith \”steady\” noise primarily attempted to determine a safe eight-hour exposurelevel and an exchange rate that represented an appropriate trade-off of higher intensityfor shorter time. Studies of the harmful effects of impulse noise, by contrast looked forhearing protection criteria in terms of factors such as the peak intensity, total numberof impulses, and duration of impulses. Thus, the criteria proposed for \”steady\”noise cautioned against application to impulse noise while criteria for impulse noisewould not, by their very nature, apply to steady noise. See generally AppendixA.2-A.7.[[10]]On September 20, 1968, the Labor Department publisheda proposed standard to regulate workplace noise exposure. 33 Fed. Reg. 12458, 14259-60.This proposed standard bore very little resemblance to the present standard. It basicallyestablished a weekly average exposure limit of 85 dB for \”steady (or equivalent)noise\” and included impulse noise in its exposure calculations. It spoke of noisewith \”intervals…more than one second and…maxima less than 1 second each,\”which fits the definition of impulse noise. The proposed standard provided that such noisemaxima are to be included in the exposure calculations as if they had durations of 1second each. See generally Appendix A.8.The proposal was unfavorably received in theindustrial hygiene community. Despite this, on January 17, 1969, a few days beforePresident Johnson’s term expired, the Labor Department issued a package of Walsh-Healeystandards, including a noise standard very similar to that which had been proposed. 34Fed. Reg. 788, 790-91. The promulgated standard retained the exposure limit of theproposed standard and the provision that dealt with impulse noise.Before the promulgated standard became effective, itwas stayed by the new Secretary of Labor. 34 Fed. Reg. 2207 (1969). On May 20, 1969, theLabor Department issued a new noise standard that differed radically from the earlier one.34 Fed. Reg. 7946, 7948-49. Except for some subsequent corrections (35 Fed. Reg. 1015(1970)), the new standard is identical to the one at issue in this case. Major differencesbetween the earlier standard and the later standard include provisions relevant to theimpulse noise issue. The earlier standard explicitly stated that noise with maxima lessthan one second in duration and greater than one second apart, i.e., impulse noise, was tobe included in weekly exposure calculations. However, the final standard contained nosimilar provision and included a provision with no counterpart in the earlier standard–arecommended limit of 140 dB for impulse noise.The final standard strongly resembled that adopted bythe ACGIH on May 12, 1969, eight days before the final version of the Walsh-Healeystandard was adopted.[[11]] Jones was still the chairman of the ACGIH Committee; he statedthat Dr. Van Atta of the Labor Department had been aware of the workings of the Committeeand of its proposed standard, and that he had received advance copies of the final ACGIHstandard. Relevant excerpts from the ACGIH standard follow:Threshold Limit Values Noise*\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0*\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0*Continuous or intermittentThe sound level shall be determined by a sound level meter . . . operating on theA-weighting network with slow meter response. Exposure shall not exceed that shown inTable 1.Table 1Permissible Exposures Duration per Day Hours Sound level dB(A)* 8 90 6 92 4 95 3 97 2 100 1? 102 1 105 ? 107 ? 110 ? 115-C** *Sound level in decibels as measured on a standardlevel meter operating on the A-weighting network with slow meter response. **Ceiling Value_________________________________________These values apply to total time of exposure perworking day regardless of whether this is one continuous exposure or a number ofshort-term exposures but do not apply to impact or impulse type of noises.When the daily noise exposure is composed of two ormore periods of noise exposure of different levels, their combined effect should beconsidered, rather than the individual effect of each. If the sum of the followingfractions:C1\/T1 +C2\/T1+ . . . . . . . Cn\/Tnexceeds unity, then, the mixed exposure should be considered to exceed the thresholdlimit value, C1 indicates the total time of exposure at a specified noise level, and T1indicates the total time of exposure permitted at that level . . . Impulsive or impact noiseIt is recommended that exposure to impulsive orimpact noise should not exceed 140 decibels peak sound pressure level-C.This ACGIH standard is very similar to theWalsh-Healey standard ultimately promulgated by the Secretary of Labor. Indeed, the finalWalsh-Healey standard was much closer to the ACGIH standard than it was to the earlierWalsh-Healey standard that it supplanted. In particular, the most important part of thefinal Walsh-Healey standard, the table listing the permissible exposure limits, is almostidentical to the corresponding table in the ACGIH standard. The passages on impulse noiseand the cumulation formula are also nearly identical to those in the ACGIH standard. Inlight of the similarities between the two final standards, and of Jones’ testimony thatDr. Van Atta of the Labor Department was familiar with the proceedings of the ACGIHCommittee and had advance copies of its work products, we infer–as do both the Secretaryand Collier-Keyworth–that the final ACGIH standard heavily influenced the finalWalsh-Healey standard.[[12]]The Walsh-Healey standard does not state explicitlythat impulse noise is excluded, as does the ACGIH standard, and the absence of such astatement in the Walsh-Healey standard might be taken to mean that the Secretary rejectedthis aspect of the ACGIH standard, deciding to include impulse noise in Table G-16calculations. However, the final Walsh-Healey standard also does not state explicitly thatimpulse noise is included in such calculations. In this critical respect, it departed fromthe earlier Walsh-Healey standard, which expressly included impulse noise. Moreover, thefinal Walsh-Healey standard contained the impulse noise provision and subsection (b)(2),both of which suggest that impulse noise was to be excluded from Table G-16.Although we cannot determine solely from thestandard’s legislative history to this point whether the Secretary intended impulse noiseto be included in Table G-16 calculations, it does reveal several highly significantfacts: Many of the scientists and organizations whose attempts to develop criteria fornoise were cited by the ACGIH Committee and the Inter-Society Committee did not believe iteither necessary or appropriate for the criteria they developed for steady or continuousnoise to apply to impulse noise. Indeed, it appears that the preponderant thinking in thescientific community that was cited by the ACGIH Committee and the Inter-Society Committeewas to exclude impulse noise from criteria for steady noise. The Labor Department wasevidently aware of this, for its technical expert on noise served on the Inter-SocietyCommittee and was aware of the views of and the limits developed by the ACGIH Committee.The standard it adopted drew heavily on the work of the ACGIH Committee and, indirectly,that of the Inter-Society Committee. There is also strong evidence that the Department ofLabor agreed with the body of scientific opinion cited by the ACGIH Committee and theInter-Society Committee.On December 4, 1970, after the noise standard wasadopted under the Walsh-Healey Act, the Labor Department’s Bureau of Labor Standardspublished Bulletin 334, Guidelines to the Department of Labor’s Occupational NoiseStandards for Federal Supply Contracts (Dec. 4, 1970), a detailed manual explaining togovernment contractors what their duties were. The 1970 version[[13]] of Bulletin 334states in part:Table 1 [equivalent to Table G-16] indicates[excessive noise] . . . . Employees must not be exposed to steady sound levels above 115dBA, regardless of the duration.*\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0*\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0*. . . The \”slow\” response [on the sound level meter] is another setting . . .which causes it to average out high level noise of brief duration (such as hammering),rather than responding to the individual impact noises.*\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0*\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0*Impulse or Impact NoiseThe last sentence in paragraph (d) of section50-204.10 states:\”Exposure to impulsive or impact noise should not exceed 140 dB peak soundpressure level.\”This sets the upper limit of sound level to which a person should be exposed,regardless of the brevity of the exposure.In contrast with the 115 dBA upper limit for steady noise, the higher intensity forimpact noise is permissible because the noise impulse resulting from impacts, like hammerblows or explosive processes, is past before the ear has time to react fully. Impact noiselevels are to be measured only with an impact meter or an oscilloscope.*\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0*\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0*Variable NoisesParagraph (c) of section 50-204.10 states the finalconsideration in determining whether or not a permissible sound level is being exceeded:\”(c) If the variations in noise level involve maxima at intervals of 1 second orless, it is to be considered continuous.\”This means that where the sound level meter on the A scale at slow response moves up froma generally steady reading, say from 88 to 92 dB, at intervals of one second or less, thehigh reading shall be taken as that to be used in Table 1 [equivalent to Table G-16].As a corollary to this, intermittent sounds of brief duration at intervals greaterthan one second should, as far as practical, be measured as to intensity and duration andthe total duration over a day be ascertained. This total should be entered in the equationgiven in footnote 1, Table 1, to determine the permissible limit. These intermittentsounds, which can be measured with a sound level meter, should not be confused withimpulse sounds of very short duration resulting from impacts or explosions.Id. at 2, 6-7 (emphasis added).Bulletin 334 went on to state that noise levels wereto be measured with a sound level meter, set for A scale and slow response, meeting thespecifications for sound level meters established by the American National StandardsInstitute (ANSI) in ANSI S1.4-1961, \”Specification for General-Purpose Sound LevelMeters.\” Bulletin 334 at 14. This ANSI standard contains the following provisions:Introduction *\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0*\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0*It should also be recognized that the ballistics and other characteristics of theindicating instrument are adapted mainly for measuring ordinary machinery noises and othersounds of a reasonably constant character. For intermittent sounds, and more particularlyfor repetitious sounds involving high peak-to-average ratios in sound pressure, and forimpact noises, other specialized equipment will be required in place of the ordinaryindicating instrument.ANSI S1.4-1961 at p. 6 (emphasis added).Several significant points emerge from Bulletin 334.The explanation of why a higher peak level is permitted for impulse noise than for steadynoise–that the ear does not react fully to impulse noise–supplies a reason why impulsenoise would be excluded from Table G-16. The statement indicates that the Secretary wasaware of the scientific reasons why the investigators who had developed criteria by 1969for steady noise did not apply their criteria to impulse noise. The instruction inBulletin 334 about including \”intermittent sounds of brief duration\” in dosagecalculations, coupled with the caveat against confusing such sounds with impulse noise, istantamount to an explicit statement that impulse noise is to be excluded from suchcalculations. Finally, the provision in ANSI S1.4-1961 that standard sound level meterscannot be used to measure impulse noise, together with the statement in Bulletin 334 thatsound level meters used for noise surveys must conform to ANSI S1.4-1961, is a furtherindication that impulse noise is excluded from the standard except for the 140 dB peaklevel provision.[[14]]C. OSHA’s Enforcement and Later InterpretationsThe record also shows that it was OSHA’s practice toexclude impulse noise from Table G-16 calculations when enforcing the standard. Anne Hart,the OSHA industrial hygienist who inspected ColIier-Keyworth’s plant, answered\”no\” when asked, \”[y]ou are not supposed to include impulse noise in yourdosimeter or sound level meter measurements, are you?\” Thomas Rockwell, an expert innoise measurement and control and a consultant to numerous corporations, testified that hewrote a letter to the Cleveland Area Office of OSHA asking if he was correct inunderstanding that the standard excluded impulse noise, and received in response a phonecall from Fred Boelter, an industrial hygienist in the Chicago office, confirming thatunderstanding. We also note that Dr. John Barry, a noise expert employed by OSHA since1976, wrote in a paper presented at Purdue University in 1979: \”This standard [29C.F.R. ? 1910.95(a)-(b)] sets the permissible exposure level for non-impulse noise at 90dBA for an 8-hour-per-day duration and less than or equal to 140 dB peak sound pressurelevel for impulse noise irrespective of its duration.\”[[15]]Dr. Barry also was the principal author of a documentinstructing OSHA industrial hygienists in the proper techniques for determining compliancewith the standard. This document was first published on April 2, 1979, as OSHA InstructionCPL 2-2.20 and was later incorporated in OSHA’s Industrial Hygiene Field Operations Manual(\”IHFOM\”) as Chapter IV.[[16]] Section C.1.e. provided:Where both continuous and impulse noise are present,measure the background on the dBA fast mode to determine if the continuous noise is abovethe levels found in Table G-16, 29 C.F.R. ? 1910.95.Thus, OSHA instructed its inspectors to determine whether the continuous component alonein a mixture of continuous and impulse noise exceeded the limits of Table G-16. Hart’sacknowledgment that she was not supposed to include impulse noise in dosage measurementstherefore reflected an official, agency-wide practice.[[17]]Our understanding of OSHA’s early enforcementpractices is further aided by OSHA’s comprehensive proposal in 1974 to completely replacesection 1910.95 with a more precise standard. The standard that OSHA then proposed and theexplanation accompanying it indicate that OSHA did not view the existing standard asincluding impulse noise in dosage calculations. The proposed standard would have retainedthe 90 dBA limit in the existing standard but would have coupled that limit withrequirements for a stringent hearing conservation program when the eight-hour timeweighted average noise level exceeded 85 dBA. 39 Fed. Reg. 37773, 37774 (Oct. 24, 1974).Although OSHA proposed to retain the 90 dBA limit at which engineering controls,administrative controls, and personal protective equipment were required, it proposed todraw a sharp distinction between steady-state noise and impulse noise, explicitlyexcluding the latter from dosage calculations. The proposed standard provided in part:? 1910.95 Occupational noise exposure.*\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0*\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0*(c) Permissible exposure limits.–\u00a0\u00a0\u00a0 (1) Steady state noise–single level. (i) Thepermissible exposure to continuous noise shall not exceed an eight-hour time-weightedaverage of 90 dBA with a doubling rate of 5 dBA. For discrete permissible . . . limits,refer to Table G-16a [omitted, similar to Table G-16].\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 (ii) Where Table G-16a does not reflectactual exposure times and levels, the permissible exposure to continuous noise at a singlelevel shall not exceed [an amount determined by a given formula] where \”L\” isthe workplace sound level measured in dBA on the slow scale of a standard sound levelmeter . . . .\u00a0\u00a0\u00a0 (2) Steady state noise–two or more levels.Exposures to continuous noise at two or more levels may not exceed [a dose computed by thecumulation formula] where C is the actual duration of . . . a given steady state noiselevel . . . . \u00a0\u00a0\u00a0 (3) Maximum steady state noise level. Exposure tocontinuous noise shall not exceed 115 dBA. . . .\u00a0\u00a0\u00a0 (4) Impulse or impact noise. (i) Exposures to impulse orimpact noise shall not exceed a peak sound pressure level of 140 dB.\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 (ii) Exposure to impulses of 140 dB shallnot exceed 100 such impulses per day.\u00a0 . . . For each decrease of 10 dB in the peaksound pressure level of the impulse, the number of impulses to which employees are exposedmay be increased by a factor of 10.39 Fed. Reg. at 37775. The preamble to the proposedstandard explained why OSHA proposed to treat impulse noise in this way:The present OSHA standard recommends that impact orimpulse sounds not exceed a peak sound pressure level of 140 dB. The Advisory Committeesuggested that this limit be made mandatory. OSHA has made an addition to the AdvisoryCommittee’s recommendation with respect to impulse noise exposure, because the actualexposure is a summation of the peak sound levels of the impulses and the number ofimpulses. OSHA proposes to limit exposure to impulses at 140 dB to 100 per day and topermit a tenfold increase in the number of impulses for each 10 dB decrease in the peakpressure of the impulse. For example, the number of impulses allowed at 130 dB would be1,000 per day and the number of impulses allowed at 120 dB would be 10,000 per day.39 Fed. Reg. at 37774. Although the proposed standardthus specified separate exposure limits for steady-state noise and impulse noise, itspreamble gave no indication that OSHA considered the proposed standard a departure fromthe existing standard. Indeed, its explanation of the proposed standard indicates thatOSHA viewed the 140 dB peak limit as being the only provision in the existing standardaddressed to impulse noise. While this falls somewhat short of being a formalinterpretation of the existing standard, it supplements the other evidence tending to showthat OSHA had interpreted the existing standard to exclude impulse noise from Table G-16.The Secretary asserts that it was not his customarypractice to exclude impulse noise from Table G-16. He cites Turner Co., 76 OSAHRC108\/A2, 4 BNA OSHC 1554, 1976-77 CCH OSHD ? 21,023 (No. 3635, 1976), rev’d on othergrounds, 561 F.2d 82 (7th Cir. 1977), as an example of a case where a citation basedon impulse noise from power presses was issued and affirmed. Turner does notsupport the Secretary’s argument. The impulse noise issue was not raised in Turnerand the parties stipulated that the noise levels exceeded those permitted by Table G-16. 4BNA OSHC at 1556, 1976-77 CCH OSHD at p. 25,274. Moreover, power press noise is notinevitably impulse noise. If the noise maxima occur more frequently than once per second,a situation that may well have been the case in Turner,[[18]] the noise is definedas continuous by subsection (b)(2) of the standard. In any event, even if Turnerdid involve impulse noise, a single citation does not show an enforcement policy and doesnot rebut the otherwise overwhelming evidence that OSHA interpreted the standard toexclude impulse noise from Table G-16.Bulletin 334 is nearly contemporaneous with theadoption of the standard, consistent with OSHA’s early enforcement policy, and thereforelikely to reflect the understanding of those in OSHA who drafted the standard. We cannot,however, say the same of the arguments in the Secretary’s brief. The Commission hasgenerally not considered interpretations of standards in the Secretary’s brief to beauthoritative. E.g., C. F. & I. Steel Corp., 86 OSAHRC ____, 12 BNA OSHC2067, 2074, 1986 CCH OSHD ? 27,691, pp. 36,139-40 (No. 79-4786, 1986). It has Iong beenthe experience of the Commission that interpretations advanced before the Commission inthe Secretary’s briefs often are interpretations made to support litigation positions.They are not necessarily interpretations traceable to the intent of the standard’sdrafters. Id.; see Investment Company Institute v. Camp, 401 U.S.617, 626-28 (1971)(counsel’s efforts in litigation are \”hardly tantamount to anadministrative interpretation\” of a statute). This is a vital distinction, for it isthe drafters of a standard who incorporate into it the policies and compromises that therulemaking record demonstrates are appropriate. To give weight to an administrativeinterpretation not traceable to the standard’s drafters would effectively permit theSecretary to amend the standard without the safeguards mandated by Congress to affordpersons affected by the standard an opportunity to participate in the rulemaking process.The brief the Secretary filed in this case gives usno reason to believe that the interpretation it advances is traceable to the intent of thedrafters. The brief does not address subsection (b)(2) of the standard and its use of theword \”continuous.\” It does not mention Bulletin 334, or the 1974 proposedstandard and its preamble. It does not purport to have been written or reviewed by lawyerswho consulted with the drafters of the standard or who participated in the drafting of thestandard. The brief does address the 140 dB impulse noise provision but misapprehends theevents that lay behind its adoption. See note12 above. It also relies on the testimonyadduced in this litigation on the harmfulness of impulse noise and alludes to the findingsOSHA made in 1981 to support the hearing conservation amendment, though neither isevidence of what the Secretary intended when he adopted section 1910.95(a)-(b). In sum,the Secretary’s brief reflects OSHA’s current appreciation of impulse noise but providesno insight into what the Secretary of Labor intended in 1969. It is therefore entitled tono weight here.Bulletin 334 and the Secretary’s early enforcementpolicy are entitled to considerable weight, however. Bulletin 334 is \”a nearlycontemporaneous interpretation of the standard by its drafter.\” Wheeling-PittsburghSteel, 11 BNA OSHC at 1294, 1983-84 CCH OSHD at p. 33,673. Its view that impulse noiseis to be excluded from Table G-16 calculations is also reflected in OSHA’s originalenforcement policy and the understanding of OSHA officials in the 1970’s, such as Dr.Barry, who were responsible for the standard’s enforcement. And it is consistent with therationale behind the 1974 proposed standard, a document that explicitly establishedseparate limits for impulse noise and steady-state noise and gave no hint that OSHA viewedthis as a departure from the current standard.The Secretary argues that exclusion of impulse noise\”is fundamentally inconsistent with [the standard’s] goal of safeguarding humanhearing.\” That a standard addresses a problem does not mean that it was intended tosafeguard employees from it entirely. Drafters may lack enough information to justify acomprehensive treatment or to know how to write a comprehensive standard. They maytherefore decide to regulate a step at a time, going as far as their knowledge carriesthem and leaving the rest for another day. That happened here. From its text andlegislative history, from Bulletin 334 and OSHA’s early enforcement policy, we find thatthe drafters of section 1910.95(a)-(b) intended to exclude from Table G-16 impulsenoise–that is, noise with sharp energy peaks lasting less than one second and spaced morethan one second apart. We therefore vacate citation items 1a(B) and (D), and 1b(B) and(D), which are based on exposure readings of employees exposed to impulse noise.III. Noise Exposure of EmployeesThe Secretary alleges that Collier-Keyworth employeeswere exposed to noise in excess of the standard’s limits and that the company did not takethe precautions required by the standard to protect the employees. The record shows thatthe noise to which Collier-Keyworth’s employees were exposed consisted of a mixture ofnoise from the machines on which they were working and background noise that was presenteven when their machines were not operating. The background noise was purely continuousnoise, i.e., noise of unvarying or slowly varying intensity. The machine noise basicallyfalls into two categories: (1) purely impulse noise, i.e., noise with sharp energy peaksspaced at intervals greater than one second; and (2) noise resulting from impulses spacedless than one second apart, which is defined as continuous by the standard and which, forthe sake of convenience, we shall call \”quasi-continuous\” noise. To proveover-exposure, the Secretary introduced into evidence dosimeter readings that measure anaccumulated dosage from all noise present in the work environment, including impulsenoise. We have concluded, however, that pure impulse noise must be excluded frommeasurements to determine compliance with Table G-16. Thus, in evaluating the dosimeterreadings introduced by the Secretary, we must determine whether they were contaminated bysufficient impulse noise to render them unreliable measures of compliance with Table G-16levels. We find, for the reasons discussed in below, that some samples were socontaminated but that others were not, for they registrated quasi-continuous noise.Collier-Keyworth also argues, however, that dosimeters do not reliably measurequasi-continuous noise.A. The Use of Dosimeters to MeasureQuasi-Continuous NoiseCollier-Keyworth argues, and Judge Furcolo agreed,that in impulsive noise environments, the dosimeters used by OSHA may not be relied on toprove violations of Table G-16 exposure limits because they indicate noise levelssignificantly higher than the \”true noise levels.\” In making this argument, thecompany does not distinguish between pure impulse noise and quasi-continuous noise.Such a distinction must be made, however. Althoughpure impulse noise must be excluded in determining compliance with Table G-16,quasi-continuous noise is included. Dosimeter readings in environments containingsignificant amounts of pure impulse noise are inherently unreliable regardless of theaccuracy with which they measure impulse noise, for they should not be measuring suchnoise at all. They should, however, be measuring quasi-continuous noise, and the accuracywith which they measure this type of noise is critical. Thus, we must considerCollier-Keyworth’s argument to the extent it questions the accuracy with which OSHA’sdosimeters measure quasi-continuous noise.We will assume in this discussion thatCollier-Keyworth is correct in its assertion that dosimeters in impulsive noiseenvironments register dosages as if noise levels were significantly higher than the\”true noise levels.\”[[19]] However, Collier-Keyworth’s argument cannot logicallybe seen as merely an objection to dosimeters but to the standard’s prescription of theslow response mode of measurement. As we have said, a noise dosimeter is in effect a soundlevel meter with additional circuitry that automatically records dosages in the manner setout in the cumulation formula of Table G-16. And, as we shall discuss below, the circuitryof a dosimeter that arguably causes it to overcount \”true noise\” levels is notits additional dosage- calculating circuitry but the slow response circuitry it shareswith conventional sound level meters. Thus, despite the emphasis in Collier-Keyworth’sbrief on the inability of dosimeters to reliably detect \”true noise levels,\” itsargument could apply with equal force to conventional sound level meters. Indeed,Collier-Keyworth’s acoustical engineering expert, Thomas Rockwell, admitted that he wouldobtain the same results using a slow response sound level meter as a slow responsedosimeter.Dosimeters and sound level meters employing slowresponse seem to overcount the \”true noise level\” because slow responseinstruments have an integration time of one second, that is, they register an impulse asif it were spread out over a second. A burst of sound lasting one-half second wouldtherefore be displayed as if it were one second long. Because the slow responseintegration time is longer than the duration of such a noise impulse, the slow responsemode distorts the \”true\” noise pattern, making impulses appear longer induration but lower in peak intensity.[[20]]Collier-Keyworth argues that the net effect of theslow response mode is to cause dosimeters to read higher than the \”true noiselevel.\” The problem with Collier-Keyworth’s argument is that section 1910.95(a)-(b)does not regulate \”true noise levels.\” The standard regulates sound levels (1)as measured by a standard sound level meter, (2) as detected by slow response, (3) asweighed by frequency according to the A-weighting network (which weights each soundfrequency according to the car’s response to it), (4) excluding impulses more than asecond apart, and (5) treating impulses less than a second apart as continuous. Indeed, itis rather pointless to speak of \”true noise levels\” because they can never bemeasured. To measure \”true noise levels\” would require an ideal instrumenthaving, among other things, an instantaneous response time, that is, an integration timeof zero. One could build a sound level detector with a short response time, perhaps aneighth of a second, as fast response instruments have. But such an instrument would stillnot be measuring \”true noise levels.\”Inasmuch as section 1910.95(a)-(b) does not regulate\”true noise levels\” but levels as detected by slow response instruments,Collier-Keyworth’s argument is really complaint about the standard’s prescription of slowresponse. Collier-Keyworth seems to desire that sound level meters and dosimeters beemployed at fast response so as to more closely approximate the \”true level\” ofimpulse noise.[[21]] However, the standard specifies the use of slow response and whateverdeviations from true noise levels that mode introduces were within the contemplation ofits drafters. That slow response instruments give greater weight to impulse noise thanfast response instruments must be regarded as one of the many compromises that theSecretary struck when he adopted the standard. Just as the Secretary could provide thatimpulses recurring at greater than one-second intervals not be counted at all, he couldprovide for a measurement technique that gives additional weight to impulses closer thanone second together. Collier- Keyworth does not point to any illegality in the Secretary’schoice of slow response.[[22]] We therefore reject Collier-Keyworth’s arguments that slowresponse dosimeters may not be used to detect exposures greater than those permitted byTable G-16.[[23]]B. Evidence of ExposureWe now consider whether OSHA proved that anyCollier-Keyworth employee was over-exposed to quasi-continuous noise. On April 14, 1980,OSHA industrial hygienist Anne Hart began an inspection of Collier-Keyworth’s plant aimedat determining whether the company was in compliance with the noise standard. Hartattached General Radio Model 1954 dosimeters to five Collier-Keyworth employees, who worethe dosimeters throughout their work day. One of the dosimeters malfunctioned, and Hartreturned on April 18 to obtain a dosimeter reading for that employee. Hart also measuredthe noise levels in the employees’ hearing zones at various times throughout theinspection by using a sound level meter. The employees who were sampled operated powerpresses and lathes in four different areas of the plant.Presses 2208, 2209, and 2210 (citation items 1a(A))and 1b(A)) are 60-ton Bliss open-back inclinable power presses used by Collier-Keyworth tofabricate metal parts. The presses operate automatically. Sheet steel is fed into thepress bed by a feeder mechanism. A die attached to a ram above the bed descends and stampsthe part out of the stock. The part is removed from the bed by high-speed air blown out ofnozzles. The three presses were located within ten feet of each other.The presses were operated by Paul LeBlanc and NormanMelanson. The operators’ duties including changing dies, making necessary adjustments,installing coils of sheet steel stack, threading the stock into the die area, andmonitoring the operation of the presses. An operator had to be in the general area of themachines while they were operating, but the operation of each machine did not have to bemonitored closely.Using a sound level meter, Hart measured noise levelsin the vicinity of the presses ranging from 85 to 104 dBA, with readings below 90 dBAoccurring only when none of the presses were operating. The dosimeter worn by LeBlanc read305% at the end of the day, and that worn by Melanson read 286%. These readings indicatethat both employees were exposed to approximately three times the permissible dose, or,viewed a different way, that they were exposed to time-weighted average sound levels ofabout 97.6 dBA and 98.0 dBA. See 29 C.F.R. ? 1910.95, Appendix A, Table A-1 (hearingconservation standard). Hart testified that she timed the presses using a watch with asecond hand and found that the impacts for each machine were less than one second apart.She also stated that the strokes of the three machines were not synchronized, so that whenall three presses were running, the noise peaks were less than one-third second apart.Collier-Keyworth’s chief engineer, Robert Cochran,testified that the presses had a maximum stroke rate of 80 per minute. The actual strokerate was controlled automatically by the feeder mechanism and was different for each partbeing produced. Each machine was used to produce about 30 different parts. Cochran did notknow the stroke rates that corresponded to the various parts.Following the inspection, noise measurements weremade in Collier-Keyworth’s plant by experts for both parties: Thomas Rockwell forCollier-Keyworth and John Barry for the Secretary. Both experts fed the output from soundlevel meters into strip-chart recorders, which draw tracings showing how the noise levelsfluctuate with time. Tracings made by Rockwell on June 17, 1980, show press 2208 operatingat 57.5 stroke per minute, press 2209 at 48 strokes per minute, and press 2210 at 56strokes per minute. Rockwell testified that Cochran told him that the presses wereproducing some of the same parts they had been making on the day of Hart’s inspection.Under subsection (b)(2) of the standard, noise thatconsists of a series of impulses less than one second apart is treated as continuous. Thisquasi-continuous noise could be produced by a press operating at a stroke rate of morethan one per second, or sixty per minute. A press stroking slower than once per secondwill, however, generate impulse noise. Collier-Keyworth’s presses can stroke as fast aseighty per minute, but the actual rate depends on the part being produced and for someparts is slower than sixty per minute. Collier-Keyworth’s presses therefore generatequasi-continuous noise at certain times and impulse noise at other times.The evidence shows that LeBlanc and Melanson wereexposed only to quasi-continuous noise on the day of the inspection. Hart testified thatshe timed the presses and that the time between strokes was less than one second for eachpress. There is no evidence directly contradicting Hart’s testimony.[[24]]Collier-Keyworth production records showing the parts produced on the day of theinspection were introduced into evidence, but the company presented no evidence on thestroke rates that corresponded to those parts.Collier-Keyworth did show that on a later date, whenRockwell measured the noise from its presses, the presses were stroking slower than onceper second, indicating that the noise at that time was impulse noise. Moreover, Rockwelltestified that Cochran had told him that the presses were producing some of the same partswhen he was in the plant as when Hart made her inspection. However, Rockwell spent partsof three days in the plant, and the production records introduced into evidence show thatthe presses typically produced different parts on different days. Therefore, during thethree days Rockwell was in the plant, the presses probably produced several differentparts each, including some that were made during Hart’s inspection and others that werenot. In the absence of evidence that the parts produced when Rockwell made the strip chartrecordings showing the presses operating slower than once per second were the same asthose manufactured during Hart’s inspection, Rockwell’s testimony does not contradictHart’s evidence that the presses were stroking faster than once per second.We also note that it is not the noise generated by amachine, but the noise heard by an employee, that the standard regulates. During most ofLeBlanc’s and Melanson’s workday, two or three presses were operating and generatingnoise. As the presses were not synchronized, the noise maxima that they heard would haveoccurred about twice per second with two presses running and about three times per secondwith three presses operating. In any event, because each press individually producedquasi-continuous noise, two or three presses operating at the same time would also producequasi-continuous noise.Because LeBlanc and Melanson were exposed only toquasi-continuous noise, their dosimeter readings did not include any measurements ofimpulse noise. Those dosimeter readings–305% for LeBlanc and 286% for Melanson–faciallyindicate exposure that exceeds permissible limits. Collier-Keyworth asserts that a numberof factors can affect dosimeter readings, including electromagnetic fields or radio waves,wind, orientation of the microphone, chemicals, temperature effects, moisture, and noisemade by the employee wearing the dosimeter. There is no evidence, however, that any ofthese factors significantly distorted the dosimeter readings made during the OSHAinspection of Collier-Keyworth’s plant. The dosimeter readings obtained by industrialhygienist Hart are consistent with sound level meter readings she made on the day of theinspection as well as with measurements made on later days by Rockwell and Barry. Hartmeasured the noise level in LeBlanc’s hearing zone to be 99-102 dBA when LeBlanc wasstanding by press 2208 with presses 2208 and 2209, but not 2210, operating. When Melansonwas standing beside press 2209 with 2208 and 2209 running, the noise level was 100-104dBA.[[25]] At certain times, Hart measured noise levels below 90 dBA for both LeBlanc andMelanson with none of the presses running. Hart noted, however, that all three presseswere usually running during her inspection. Also, chief engineer Cochran testified thatCollier-Keyworth had no excess press capacity, indicating that the presses operatedfull-time except when dies were changed or adjustments made.As noted above, the dosimeter readings Hart obtainedfor both LeBlanc and Melanson were approximately 300% of the permitted daily dose. Anemployee exposed to a constant noise level of 100 dBA for 6 hours would receive a dosageof 300%. The sound level meter readings made by Hart show that LeBlanc and Melanson weresometimes exposed to noise levels less than 90 dBA, but were exposed to noise levelsaround 100 dBA for most of their 8-hour shifts.Thus, the sound level meter readings tend to showthat the dosimeters were accurately measuring and recording the noise levels to whichLeBlanc and Melanson were exposed.In summary, we conclude that on April 14, 1980,LeBlanc and Melanson, the operators of presses 2208, 2209, & 2210, were exposed tonoise in excess of the limits permitted by Table G-16.Press 2216 (items 1a(C) and 1b(C)) is a 60-ton BIisspress similar to the three presses discussed in the previous section but located somedistance from them. In April 18, 1980, industrial hygienist Hart attached a dosimeter topress operator Alan Sund. After 202 minutes, or about 3.3 hours, the dosimeter read 167%.Sound level meter readings made by Hart in Sund’s hearing zone at four different timesover the period the dosimeter was operating were 103-107 dBA while the press was running.Sund was then observing the machine from a distance of one to two feet. As with the otherpresses, Hart testified that she timed the stroke rate and that the time between strokeswas less than one second. On June 17, 1980, Rockwell measured the stroke rate of the pressto be 45 strokes per minute, but there is no evidence that the press was producing thesame part, and thereby running at the same speed, as during Hart’s inspection.For much the same reasons as previously discussed, wefind that the evidence shows Sund was exposed to noise exceeding the standard’s permittedlimits. Hart’s testimony that the time between strokes was less than one second on the dayof the inspection establishes that the noise was continuous within the meaning of thestandard. The dosimeter reading facially indicates that Sund was exposed to excessivenoise. The sound level meter readings indicate that Sund was exposed to 103-107 dBA forabout 3.3 hours. At 103 dBA, the lowest sound level in this range, only about 1.3 hours ofexposure is permitted. Thus, the sound level meter readings corroborate the measurement ofexcessive exposure made by the dosimeter.Press 352 (items 1a(D) and 1b(D)) is a manually-fedmachine used for small bending jobs. On April 14, 1980, Hart obtained a reading of 256%from a dosimeter attached to press operator Ernest Couture. According to Hart, the pressstroked once every two or three seconds. With the machine not operating, Hart measured thenoise in Couture’s hearing zone to be from 84 to 88 dBA. With the machine operating, shemeasured noise levels as high as 95 dBA.We conclude that the Secretary did not prove Couturewas exposed to excessive noise. Because the press stroked only once every two to threeseconds, the noise that resulted from the press’s operation was impulse noise, which isnot regulated by Table G-16. The only continuous noise to which Couture was exposed wasbackground noise measured to be 84 to 88 dBA, levels within the standard’s limits for anyexposures time. We therefore find that Couture was not exposed to noise exceeding thestandard’s limits and we will vacate items 1a(D) and 1(b)(D)).Lathes 6040 and 3018 (items 1a(B)) and 1b(B)) areused to cut metal tubing and chamfer the ends. Both lathes were operated by a singleemployee, Ken Thompson. Lathe 6040 was operated manually, while lathe 3018 was automatic.Therefore, when both lathes were operating, Thompson would be standing beside lathe 6040.On April 14, 1980, a dosimeter attached to Thompson during his shift yielded a reading of158.5%. According to sound level meter readings made by industrial hygienist Hart, thenoise level in Thompson’s hearing zone ranged from 85 to 107 dBA.Lathe 6040 was relatively quiet and, when operatedalone, produced noise levels below 90 dBA. Thus, the noise that caused the standard’slimits to be exceeded was generated by lathe 3018. That lathe sometimes emitted a veryloud high-pitched squeal, but at other times the squeal was missing. Hart recorded noiselevels of 107 dBA when the squeal was evident, but only 92 dBA with both lathes runningbut no high-pitched squeal present. When Dr. Barry later visited Collier-Keyworth’s plant,he measured 118 dBA in the hearing zone of the operator of lathe 3018. Upon analyzing thefrequencies contained in the noise, Barry found that the excessive noise primarilyoccurred at 8000 hertz and higher, frequencies which the human ear would perceive as veryhigh.Both Barry and Rockwell made strip chart recordingsof the lathe noise. These recordings show very pronounced short bursts of noise, much likethe strip chart recordings for the power presses. The charts are not labeled with timescales that would enable the time between bursts to be measured, but Rockwell testifiedthat the charts show a peak-to-peak separation greater than one second, indicating that atleast some of the noise is impulse noise.We conclude that the Secretary failed to proveThompson was exposed to excessive noise. Some of the noise to which Thompson was exposed,and which was detected by the dosimeter, was impulse noise that must be excluded under thestandard. There is no basis to conclude that Thompson’s dosimeter reading would have shownoverexposure if the impulse noise had been excluded. Indeed, it is doubtful that theSecretary proved overexposure even assuming that impulse noise were to be included.Industrial hygienist Hart testified that Type 2 sound level meters and dosimeters, thetype she used in her inspection, generally have an inherent error factor of two dBA; whenthat error is cumulated over time, it creates a potential error of 32% in the dosimeterreading.[[26]] Thus, a dosimeter reading of 158.5%, as was obtained for Thompson, wouldgenerally be outside the instrument’s range of error and would show overexposure. However,the record shows that the noise to which Thompson was exposed was of very high frequency,predominantly 8000 hertz. At 8000 hertz, type 2 sound level meters and dosimeters have aninherent error factor of 6.5 dBA.[[27]] This means that a dosimeter containing a type 2sound level meter would have to read over 240% to show overexposure once the inherenterror of the instrument at 8,000 hertz is taken into account. Cf. 29 C.F.R. ? 1910.95,Appendix A, Table A-1 (hearing conservation standard)(entry for 96.3 dBA corresponds todose of 240 percent). Thus, where the noise is predominantly at 8000 hertz, a dosimeterreading of 158.5%, the reading obtained for Thompson, does not show overexposure withinthe accuracy limit of the instrument.We therefore vacate citation items 1a(B) and (D), and1b(B) and (D). Having found that OSHA proved over-exposure to quasi-continuous noise bypress operators LeBlanc, Melanson and Sund–the employees involved in items 1a(A) and (C),and 1b(A) and (B)–we must now determine whether the Secretary showed thatCollier-Keyworth violated the standard by failing to take required precautions againstexcessive noise exposure.IV. Precautions Against Noise ExposureThe Secretary alleges in citation item 1a thatCollier-Keyworth violated section 1910.95(a) by failing to enforce the use of hearingprotection equipment. In item 1b, he alleges that the company violated section1910.95(b)(1) by failing to implement feasible administrative or engineering controls toreduce noise exposures.[[28]]A. Personal Protective Equipment–Subsection1910.95(a)Citation items 1a(A) and (C) concern the allegedfailures by the three employees to wear personal hearing protectors. Industrial hygienistHart observed LeBlanc and Melanson wearing earmuffs and Sund wearing Swedish wool earplugsduring her inspection. Hart testified, however, that she also observed the employees\”at one time or another\” not wearing hearing protection. The Secretary relies onHart’s testimony that she observed the employees without hearing protection to support hisallegation under section 1910.95(a).The evidence does not prove that Collier-Keyworthviolated section 1910. 95(a). Under the standard, employees may be exposed to noise levelsless than 115 dBA for some period of time without using protective equipment. Also, atvarious times the three employees were subjected to noise levels less than 90 dBA, whereno protection is required regardless of the length of exposure. Thus, Hart’s testimonythat she observed the employees at times without protection does not prove a violation ofthe standard. If anything, the evidence that the employees were sometimes observed wearinghearing protection tends to show that Collier- Keyworth complied with section 1910.95(a).We therefore vacate citation items 1a(A) and (C).B. Engineering Controls–Subsection 1910.95(b)(1)The Secretary alleges in citation item 1b(A) and (C)that Collier-Keyworth violated section 1910.95(b)(1) by failing to implement feasibleengineering controls on presses 2208, 2209, 2210, and 2216.[[29]] His expert witness onengineering controls, Dr. Barry, proposed two basic noise reduction techniques he believedwere feasible: enclosing the die areas on the presses; and replacing the existing airejection nozzles with quieter ones.Each press forms metal parts by the force exerted bya rapidly descending die on sheet steel in the bed of the press. Barry testified thatthere were two primary sources of noise associated with the operation of a press: (1)noise from the impact of the die on the sheet metal stock; and (2) noise from the airejection nozzles used to expel the parts from the press bed. Barry recommended isolatingthe press operators from the noise sources by installing acoustical enclosures around thedie areas of the presses.[[30]] He testified that the enclosures would have to be designed\”to minimize any operator encumbrances and allow for ease of die change.\” Theenclosures, in Barry’s opinion, should be made of sheet metal, with transparent plasticpanels to permit visual observation of the die area. Doors and openings should be tightlysealed, and the inside of the enclosure should be lined with acoustically absorptivematerial to prevent sound buildup. Barry believed that each press enclosure would cost$3,500 to $4,000 to design, fabricate, and install, and that a reduction in noise level of10 dBA could be achieved. Barry had seen similar enclosures in use at another company’splant and believed those enclosures achieved a 10 dBA reduction without inhibitingproduction.The enclosures Barry recommended would enclose theair ejection nozzles as well as the die impact area, and would therefore reduce noise fromboth sources. Barry also testified that the air noise could be reduced even if the diearea were not enclosed. Either quieter nozzles that were commercially available couldreplace the existing nozzles, or the velocity of air from the existing nozzles could bereduced to lessen the noise. Barry stated that the commercial nozzles would cost $5 to $20each and would, in his opinion, produce a significant reduction in the noise level. Curtis Holmer, a noise control engineer who testifiedfor Collier-Keyworth, did not believe that enclosing the die areas of the presses wouldsignificantly reduce the impact noise emanating from the presses. Holmer testified thatenclosing the die area can significantly reduce the noise from a press only when the forcethe press exerts is considerably below its capacity. However, when a press is used at ornear its capacity, as the presses were at Collier-Keyworth, then most of the energy of theimpact is transferred from the die area to the frame of the press, and most of the noisethe press produces radiates from its frame instead of from the point of impact. Holmertherefore believed that enclosing the die area alone, as recommended by Barry, would notreduce the noise resulting from the impact of the die on the stock. The enclosures wouldreduce only the air ejection noise, and Holmer thought this noise reduction would be onthe order of 3 dBA or less.Chief Engineer Cochran testified that die enclosureswould severely restrict the productivity of the presses by increasing the time necessaryfor the operators to perform any duty requiring access to the die area. Cochran reviewedthe production reports prepared by the operators for a four-week period to determine howoften they needed access to the die area. Estimating that each instance of access wouldrequire 30 extra minutes if the dies were enclosed, he calculated that the company wouldhave lost 72 hours of production over the four-week period, or about 950 hours for ayear.[[31]] Since the company had no excess press capacity, it would have to purchase anew press to maintain its current level of productivity. According to Cochran, a new presswould cost $55,000. A plant addition to house the machine would cost an additional$18,000, and a new operator would have to be hired to run the machine at a cost of $24,000per year. Cochran also noted that the data on which he based these estimates mightunderstate the number of times the operators needed access to the dies because theoperators might not record situations that were now very easy to resolve, such as clearingout a piece of scrap from the die area.Regarding Barry’s suggestion that the existing airejection nozzles be replaced with quieter ones, plant engineer English testified that thecompany had tried using quieter nozzles in 1977 but that those nozzles reduced the airvelocity below what was needed to eject the parts from the press bed. Curtis explainedthat quiet nozzles obtain their noise reduction by reducing the air velocity and byspreading out the air stream over a larger area. However, for small parts such asCollier-Keyworth made, much of the air from such nozzles would blow past the part and beineffective in moving it.In Sherwin-Williams, 11 BNA OSHD at 2110,1984-85 CCH OSHD at p. 34,702, the Commission stated what the Secretary must prove to showa violation of section 1910.95(b)(1):To prove a violation, therefore, the Secretary mustprove that proposed engineering and administrative controls are both technologically andeconomically feasible. As the Ninth Circuit recognized in Castle & Cooke,\”realism and common sense should dictate how the Secretary may meet his burden ofproviding substantial evidence of feasibility.\” 692 F.2d at 650. After the Secretaryproves that controls are technologically feasible, the burden of producing evidence shiftsto the employer, who may raise the issue of economic feasibility and go forward withevidence of the cost of controls and personal protective equipment. The burden ofproducing evidence then returns to the Secretary, \”who must establish that thebenefit of the proposed engineering controls justifies their relative cost in comparisonto other abatement methods.\” Id. The ultimate burden of persuasion on thefeasibility issue nevertheless remains with the Secretary.The Secretary clearly did not prove the feasibilityof reducing the air ejection noise by installing quieter nozzles. Although quieter nozzlesare commercially available, Collier-Keyworth had tried such nozzles several years beforethe alleged violation and found that the reduced velocity of air they produced providedinsufficient force to eject the parts from the die area. Thus, such nozzles would notaccomplish their intended purpose and would be technologically infeasible.We also find that the Secretary failed to prove thefeasibility of die enclosures. The enclosures would produce a minimal benefit insufficientto justify substantial cost.The enclosures Barry recommended would surround thedie areas of the presses and isolate the operators from the noise produced by the impactof the die on the stock and the noise from the air ejection nozzles. Barry believed thatsuch enclosures could reduce noise levels about 10 dBA. Collier-Keyworth’s expert, Holmer,testified that the enclosures would produce only about a 3 dBA reduction. In Holmer’sview, the die enclosures would only reduce the air ejection noise reaching the operators,and not the noise from the die striking the stock.We give considerable weight to Holmer’s opinion.Holmer had lengthy experience in the measurement and control of industrial noise and was amember of the Institute of Noise Control Engineering, a national organization of competentnoise control professionals. He provided a reasoned explanation for his conclusion thatdie enclosures on Collier-Keyworth’s presses would not substantially reduce impact noiseand we find his testimony persuasive. Barry’s opinion that enclosures could achieve a 10dBA reduction is entitled to much less weight than HoImer’s. Barry’s training wasprimarily in measuring the effects of noise on the human ear rather than the analysis andreduction of industrial noise by engineering means. Barry had not designed or implementedindustrial noise controls and was not a member of the Institute of Noise ControlEngineering. Moreover, Barry’s opinion was based only on his belief that die enclosures atanother company had achieved a 10 dBA reduction. Holmer’s testimony indicates, however,that the noise reduction produced by a die enclosure depends on the degree of capacity atwhich the press is used. Thus, achievement of a 10 dBA reduction at another company, inthe absence of evidence of similar conditions, is a tenuous basis for believing thatCollier-Keyworth could obtain a comparable reduction. We find that the die enclosuresrecommended by Barry would achieve a reduction of about 3 dBA in the noise levels to whichCollier-Keyworth’s press operators were subjected.A reduction of 3 dBA is significant (see ContinentalCan Co., 76 OSAHRC 109\/A2, 4 BNA OSHC 1541, 1543 n. 8, 1976-77 CCH OSHD ? 21,009, p.25,253 n. 8 (No. 3973, 1976)), but it must be balanced against the costs of engineeringcontrols and considered in light of other protective methods. See Sherwin-Williams,11 BNA OSHC at 2110, 1984-85 CCH OSHD at p. 34,702. The other method that we consideredhere is the personal protective equipment that Collier-Keyworth’s employees now wear. Dr.Victor Hildyard, a medical doctor specializing in diagnosis and treatment of diseases ofthe ear, testified that earplugs and earmuffs of the type used by Collier-Keyworth’semployees could reduce the noise reaching the employee’s inner ear by 30 dBA if wornproperly. Even if loosely fitted, the equipment would reduce noise levels by 10-15 dBA.Thus according to Dr. Hildyard, a noise reduction of 10 dBA is readily achievable even ifthe performance of the equipment is far less than ideal. The highest time-weighted averagesound level to which Collier-Keyworth’s press operators was exposed was about 98dBA.[[32]] Thus, if engineering controls were not required at all, the personal protectiveequipment would very likely meet Collier-Keyworth’s obligation under section 1910.95(b) to\”reduce sound levels within the levels of the table.\” Yet, even if engineeringcontrols were installed, the employees would still have to wear the personal hearingprotectors because a 3 dBA reduction would not reduce noise to within Table G-16 limits.They would simply not have to wear it for as long as they now must. Thus, installing dieenclosures would not eliminate the need for personal protective equipment but would onlydecrease the amount of time employees must wear it.The cost of the controls is, however, substantial.According to Barry, each enclosure would cost $3,500 to $4,000 to design, fabricate, andinstall. Moreover, to maintain its current level of production, Collier-Keyworth wouldhave to purchase a new press for $55,000, and would incur additional costs associated withthe new press, including a die enclosure for that press as well. The new press would add anoise source to Collier-Keyworth’s plant and could result in additional noise exposure forsome employees. On balance, we are not convinced that the benefits to be gained from theenclosures justify these costs. We therefore find that the die enclosures recommended byBarry were not shown to be feasible and will vacate citation items 1b(A) and (C).Accordingly, we vacate citations item 1a(B) and (D),and 1b(B) and (D), which involve employee exposure to impulse noise, unless the Secretaryrequests an opportunity within 15 days of this decision to rebut officially-noteddocuments with evidence of the Secretary’s intent in 1969. We vacate items 1a(A) and (C)because the Secretary failed to show that employees were not wearing personal hearingprotectors for the periods required. And we vacate items 1b(A) and (C) because theSecretary failed to show that proposed engineering controls were feasible. The judge’sdecision is therefore affirmed.FOR THE COMMISSIONRay H. Darling, Jr.Executive SecretaryDATED: April 6, 1987Appendix1. The noise standard proposed by the ACGIH committeein 1968 stated in part: Average Sound Pressure Levels of Octave Bands with Center Frequencies of 500, 1000, and 2000 Hz A-Weighting Network of Sound Level Meter Duration of Exposure per Day dB dBA Hours 85 92 4 – 8 90 97 2 – 4 95 102 1 – 2 100 107 less than 1 hour These values apply to total time of exposure per working day regardless of whether this isone continuous exposure or a number of short-term exposures but does [sic] not apply toimpact or impulsive type of noises.When the daily noise exposure is composed of two ormore periods of noise exposure of different levels, their combined effect should beconsidered, rather than the individual effect of each. If the sum of the followingfractions:C1\/T1 + C2\/T2+ . . . Cn\/Tnexceeds unity, then, the mixed exposure should beconsidered to exceed the threshold limit value[.] C1 indicates the total timeof exposure at a specified noise level, and T1 indicates the total time ofexposure permitted at that level.*\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0*\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0*The above limits do not apply to impose or impact type of noise. It is recommendedthat exposure to this type of noise should not exceed 140 dB peak sound pressure level.Appendix 1 of Herbert H. Jones, \”ACGIH’sProposed Threshold Limit Value for Noise,\” 29 Am. Indus. Hygiene J. 537-40 (Nov.-Dec.1968)(ACGIH).2. A paper cited by both the Inter-Society Committeeand the ACGIH Committee and that proposed criteria for steady noise concluded with thefollowing observation:We have purposely omitted any discussion of impulse noise up to now, for very soundreasons. We know very little about the effects of impulse noise on the ear. We have juststarted an intensive study of the relations between impulse noise and TTS [temporarythreshold shifts, a form of hearing loss].The problem does not lend itself to easy solution,for several reasons. Measuring impulse noise is difficult to begin with, but not nearly asdifficult to resolve as determining the effect the middle ear muscles have on thetransmission of impulsive noise across the middle ear. Limited laboratory researchindicates that the laws governing TTS from exposure to steady noise (non-impulse) do notoperate for impulsive noise exposure. Actually, this should not be surprising, since theresponse of the basilar membrane to steady noise and to impulse noise should be completelydifferent.For the present, we can only say that no one shouldbe habitually exposed to impulse noise of any considerable magnitude without the use ofhearing conservation measures.*\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0*\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0*Our very limited knowledge of the effects of impulse noise prevents any meaningfuldiscussion of impulsive-type noise exposure.A. Glorig, W.D. Ward, & J. Nixon, \”DamageRisk Criteria and Noise-Induced Hearing Loss,\” 74 Archives of Otolaryngology413, 423 (Oct. 1961), cited in I-S at 424 ref. 16; and ACGIH at 539ref. 6 (article) and at 540 ref. 6 (proposed standard).3. A later report by a subcommittee chaired by Dr.Glorig proposed criteria for hearing conservation with the following caveat:Our knowledge of the relations of hearing loss tonoise-exposure permits us to propose guidelines for establishing standards for preventingsignificant noise- induced hearing loss in the majority of exposed persons. Theserecommended standards have been proposed by the International Organization forStandardization. They are presented below in brief modified form. They do not apply toexposure to impulsive noise but only to steady noise.Subcommittee on Noise, Committee on Conservation of hearing, Am. Acad. of Ophtalmology andOtolaryngology, Guide for Conservation of Hearing in Noise 13 (1964)(emphasis inoriginal), cited in I-S at 424 ref. 9.4. A 1966 publication of the American IndustrialHygiene Association reviewed the criteria for recommended noise limits that had beenproposed by various investigators up to that time. While noting that there was littledisagreement as to the levels of continuous noise that were harmful, the publication wenton to say:Much more difficult will be the selection ofmandatory protection levels for intermittent, short duration, and impact noises . . . .Because there is still much to be learned about the relationships between temporary andpermanent threshold shifts the criteria for brief exposures cannot be expected to have thesame reliability as those for continuous exposures. Until more is known about short-timeexposures, the criteria should be treated as temporary benchmarks and be used withconsiderable judgment.Am. Indus. Hygiene Ass’n., Industrial Noise Manual,ch. 7, at 59-60 (2d ed. 1966), cited in I-S at 424 refs. 3 & 13; and ACGIHat 540 ref. 3 (proposed standard).5. A 1967 paper by Coles et al. summarized studiesthat had tried to assess damage risk from impulse noise exposure. R. Coles, G. Garinther,D. Hodge, & C. Rice, Criteria for Assessing Hearing Damage Risk From Impulse-NoiseExposure, U. S. Army Tech. Memo. 13- 67 (Aug. 1961) , cited in ACGIH at539 ref. 12 (article).[[33]] These studies tended to seek permissible exposure criteria interms of factors unique to impulse noise. Several of the studies demonstrated thatexposure to 25-100 impulses in the 140-170 dB range at 6-30 impulses per minute couldproduce temporary threshold shifts (\”TTS\”)[[34]] in a significant number ofexposed persons. The variations in the TTS’s of people exposed to such impulse noise wasgreater than among subjects exposed to steady-state noise, indicating that some people maybe particularly susceptible to impulse noise. Responses were observed to vary depending onwhether the noise reached the ear at normal or grazing incidence; in same instances, forexample, noise from a gun fired by a person near the subject, which would reach thesubject’s ear at normal incidence, appeared more harmful than noise from a gun fired by asubject himself, which would reach his ear at grazing incidence. TTS’s were greater forlonger duration impulses of similar peak intensity. a result probably attributable to thegreater energy associated with the longer impulses. The paper drew from the studiescriteria for peak pressure level and duration limits that would not produce an excessiverisk of hearing loss. It concluded that impulses in the 155-160 dB peak intensity rangewere safe for a duration of about 10 milliseconds, with higher intensity impulsespermissible for shorter duration and lower intensity impulses permissible at longerdurations.6. In a slightly later paper, the same authors notedthat it was customary in proposing damage risk criteria for steady-state noise to excludeimpulse by implication rather than by direct statement. R. Coles, G. Garinther, D. Hodge,and C. Rice, \”Hazardous Exposure to Impulse Noise,\” 43 J. Acous. Soc. 336(1968), cited in ACGIH at 539 ref. 11 (article). After discussing riskfactors associated with common amounts of exposure to gunfire, the paper said, \”themore industrial types of impulse-noise exposure as in riveting, pile driving. dropforging, etc., may require a separate criterion or may be treatable by steady-state noisecriteria.\” Id. at 339. However, the authors concluded:[w]hether a more general continuity between impulseand steady-state noise criteria can ever be achieved seems very uncertain in view of theevident differences in their ranges of TTS and of opinion such as that of Kryter andGarinther that PTS from impulse noise may follow a different pattern from PTS due tosteady-state noise. Id. at 343 (reference omitted).7. Investigators attempted to determine the combinedeffect of impulse noise and steady-state noise in only one cited study. A. Cohen, B.Kylin, and P. LaBenz, Temporary Threshold Shifts in Hearing From Exposure to Combinedlmpact\/Steady-State Noise Conditions, 40 J. Acous. Soc. 1371 (1966), cited in ACGIHat 539 ref. 10 (article). An experiment was conducted on 15 subjects. who were exposed toa variety of combinations of impulse and steady-state noise. The study found that, undersome circumstances, impulse noise in the presence of noise was less harmful to hearingthan the impulse noise alone. The authors concluded that this was due to the\”acoustic reflex,\” which is a contraction of the middle ear muscles thatattenuate, the amount of sound transmitted to the inner ear. If the acoustic reflex isactivated before exposure to a loud impulse, the inner ear receives protection from theimpulse. Therefore, when the subjects were exposed to steady noise that was loud enough toactivate the acoustic reflex, the impulse noise was not as damaging as it otherwise wouldhave been.8. The standard proposed by the Department of Laborunder the Walsh- Healey Act on September 20, 1968, at 33 Fed. Reg. 14259-60, stated:? 50-204.10 Occupational noise exposure.(a) The maximum permissible steady (or equivalent)noise level in the working environment shall not exceed 85 decibels. Every employer shallutilize every feasible engineering method to control noise levels. Such methods of controlinclude reducing the amount of noise produced at the source, reducing the amounttransmitted through the air, and substituting quieter procedures or machinery.(b) Where the noise is not steady the equivalent steady noise level is determined bythe following procedure: The duration over 1 week of each clearly distinguishable soundlevel is located in column 1 of Table I following this paragraph (b) and the partial noiseexposure is read at the intersection of this row with the appropriate sound level column.The partial noise exposures thus obtained are added arithmetically. The sum is thecomposite noise exposure. The continuous noise exposure equivalent to the composite noiseexposure is then read from Table II next following Table I. If the variations in noiselevel involve maxima at intervals of 1 second or less it is to be considered steady. Ifthe intervals are more than one second and the duration of the maxima are less than 1second each, maximum is to be considered as 1 second.THE PICTORIAL EXHIBIT REFERRED TO ABOVE IS NOT AVAILABLE IN THIS FORMAT.\u00a0 PLEASETELEPHONE THE REVIEW COMMISSION PUBLIC INFORMATION OFFICE, 202-606-5398, TO REQUEST APAPER COPY; TTY: 202-606-5386; FAX: 202-606-5050; E-MAIL: [email protected] \u00a0SECRETARY OF LABOR, Complainant, v. COLLIER-KEYWORTH CO., Respondent.OSHRC DOCKET NO. 80-2848APPEARANCES:Robert Yetman, Esq., for ComplainantDouglas B. M. Ehlke, Esq., for RespondentDECISION AND ORDERThis is a proceeding pursuant to the OccupationalSafety & Health Act of 1970, as amended (29 USC, sec. 651 et seq.)hereinafter called the Act. The Complainant alleges that the Respondent has violated sec.5(a)(2) of the Act (sec. 654) by not complying with the Occupational Safety & Healthstandards.The Respondent is a corporation engaged in thebusiness of manufacturing chair mechanisms and its business affects the commerce of theUnited States.The Respondent’s worksite at Gardner, Massachusetts,was inspected by the Occupational Safety & Health Administration (hereinafter calledOSHA) on or about April 9 – 18, 1980.On or about April 28, 1980, the following Citation,together with Notice of Proposed Penalty, was issued against the Respondent: Citation #1,Items #1a – c, the serious violation of the standards at 29 CFR 1910.95(a), .95(b)(1), and.95 (b)(3); respectively Items 1a, b, and c of Citation #1.On May 16, 1980, the Respondent filed Notice ofContest to Items #1a – c of Citation #1 and the penalty proposed therefor.In his post-hearing brief, the Complainant withdrewitem 1(c).The pertinent words of the standards and the Act areappended to this decision under appropriate titles. The basic issue is whether or not theRespondent’s employees were exposed to noise exceeding the limits of Table G-16 of thestandard at 29 CFR 1910.95(a).SINCE THE HEARINGS WERE HELD ON MARCH 23 – 27, JUNE16 – 19, DECEMBER 8 – 11 [ALL IN 1981] AND MARCH 23 and 24, 1982, THE 1981 TRANSCRIPT WILLBE REFERRED TO BY MONTH AND PAGE NUMBER [E.G., MARCH 225] AND THE 1982 TRANSCRIPT BY YEAR,MONTH, AND PAGE NUMBER BECAUSE SOME OF THE TRANSCRIPT PAGES ARE NUMBERED THE SAME EVENTHOUGH THEY COVER DIFFERENT DATES.It was a very long and hard-fought case, involvingmany scientific treatises and expert testimony. Both attorneys are to be commended fortheir excellent preparation and the zeal with which they tried the case.PRELIMINARYUnless otherwise indicated, the word\”dosimeter\” [as used herein] refers to the Gen Rad 1954 type 2 instrument usedin the April inspection of the Respondent’s jobsite. The dosimeter has an integrator that\”counts\” the sound waves that constitute noise; and it has a 5dB rate ofexchange as distinguished from a 3dB one. A \”decibel\” is roughly understood as aunit for expressing the relative intensity of sound. The integrator may be\”slow\” [a time constant of 1 second] or \”fast\” [a time constant of1\/8th of a second]. The slow integrator is considered to be less accurate than the fast infollowing the quick noise…Tr. June 1147-1150. The jobsite was inspected in April of 1980. Themachines cited were punch presses [#’s 2208, 2209, 2210 on the second floor annex, #0352on the 4th floor, and #2216 on the 2nd floor of the steel warehouse] and two lathes [#6040and #3E 3018, both in the torsion department]. The sound levels were obtained through theuse of a dosimeter operated by or under the supervision of OSHA Industrial Hygienist AnneHart.In measuring sound for the purposes of Table G-16 ofthe standard at 29 CFR 1910.95(a) – (b)(3), a dosimeter at slow response with a 5dB rateof exchange is used because the standard mandates a \”slow\” response. Theevidence indicated that a different race of exchange [e.g., 3dB] would not qualify as a\”slow\” response; but, on the other hand, a different rate of exchange might bemore accurate for certain types of sound. One of the issues in the case was whether the5dB rate of exchange would disclose the true level of sound if fluctuating or impulse[impact] noise were also present. \”Exchange rate\” is the relationship betweennoise level and duration. To illustrate: a 5dB exchange rate means that the sound levelcan be increased by 5dB with every halving of exposure duration.There are two sets of dates on which soundmeasurements were taken by the Complainant: those in April, to which OSHC ComplianceOfficers Goyda and Hart testified; and those in September, to which sound expert Barrytestified. The witness Rockwell took sound measurements in February of 1981; and thewitnesses Jones, Kamperman, Holmer, Kundert, and Botsford apparently did not participatein actual measurements of the cited machines but testified as sound experts.IMPULSE NOISEThe case required considerable evidence of a highlytechnical nature involving sound level meters, dosimeters, 3bB and 5dB rates of exchange,various kinds of noise, etc. A basic issue concerned impulse noise.Several questions about impulse [or impact] noisemust be resolved: What is it? Did it exist in the cited machines? Was it accuratelymeasured by the dosimeters used in the inspection? Should it have been included orexcluded in the dosimeter readout to determine compliance with Table G-16?TESTIMONYGoydaThe Witness Goyda, who is an experienced andcompetent Compliance Officer, was a member of the OSHA inspection party. He monitored thedosimeter testing in April of the employee, Couture . . . Exh. C-1. I was impressed withhis competence and honesty. I find that he accurately reported the readout registered bythe dosimeter, as recorded in Exh. C-1.HartThe witness Hart, who is an experienced and competentIndustrial Hygienist, was in charge of the April inspection of the jobsite. She calibratedthe dosimeters used, directed the placing of dosimeters on employees, and recorded orsupervised the recording of their readouts. . .Tr. June 672 – 685. I was impressed withher competence and honesty. I find that she followed proper procedures in testing and thatshe accurately reported the readouts registered by the dosimeters, as recorded in Exh. C1- 5.She testified that the testing instrument was a GenRad 1954 Type 2 dosimeter, slow response, A weighted. . .Tr. June 730, 733. She said thatimpulse noise is not supposed to be included in the dosimeter measurement because thereading will be distorted and will inaccurately register higher. . .Tr. June 768-770. Shealso testified that there was impulse noise from press #0352. . .Tr. June 715, 716.Exh. C-1 – 5 reflect that the sound levels recordedduring the April inspection ranged from 94 to 101.3dBA as related to Table G-16.BarryThe expert Barry, who was called by the Complainant,was well-qualified. . .Tr. March 319 – 324, Exh. C-20. He testified that the effects ofimpulse noise are not supposed to be excluded; and that Table G-16 has no relation toimpulse noise and does not exclude it. . .Tr. March 512, 513, June 913, 914, December 902.He emphatically stated that the findings of Compliance Officer Hart were reliable withcorrection factors that would not change her conclusions; and that the type dosimeter usedin her inspection was a suitable instrument for measuring noise levels to determine OSHAcompliance. . .Tr. June 952 – 958. He concluded that, even applying error factors,employees were still exposed to excessive noise. . .Tr. December 984.However, Barry also testified that the dosimeter hasbeen a controversial instrument in recent years. . .Tr. March 517, 518. He said thatdosimeters tend to register higher readings than actual noise levels; and that, for thesounds typical here, the reading could be higher by 4 or 8 decibels. . .Tr. June 953,December 939, Exh. R-60. He also said that the more impulse and the higher, the greater isthe dosimeter’s error. . .Tr. June 1008. He testified that a dosimeter’s readout might beinaccurate due to the slow response setting required by the standard because, where thereare both steady and impulse noises, the dosimeter distorts on the high side; and that theuse of both fast and slow modes of response would be better testing procedure. . .Tr. June925 – 928, 933, December 909, 910, 917, 948. He suggested that, \”to measure it reallyproperly, the standard would have to be rewritten.\”. . .Tr. June 927. It had been hisopinion [as he wrote in the OSHA Field Officer’s Manual] that, where both continuous andimpulse noise are present, the proper way to determine compliance with Table G-16 is touse the fast mode setting and record the reading between the impulses. . .Tr. June 922,923, 1015 – 1019. He had also authored an article in which he stated that the standard at29 CFR 1910.95 \”sets the permissible exposure level for non-impulse noise.\”. ..Tr. June 920. He acknowledged that he had said that Table G-16 was intended primarily fornon-impulse noise. . .Tr. December 904, 906, Exh. R-59, R-62.As concerns the 3dB and 5dB rates of exchange, heagreed that the readout would differ depending on which was used, resulting in a possibledosimeter overstatement inaccuracy of 100 – 200 percent. . .Tr. June 934 – 937. He hadalso recommended a change in the dosimeter from a 5dB exchange rate to the use of a 3dBone \”and making no differentiation between the type of noises. In other words,integrate all noise as noise. And, use that for determining compliance ornon-compliance.\”. . .Tr. June 943. While that suggestion could be explained asreferring to possible ambiguities in the standard, it could also be interpreted as abelief that the standard does exclude some noise; otherwise, why the need to specify thatall. noise is included?Barry’s testimony also indicated that there was adiscrepancy of several decibels between the slow and fast modes when he measured themachines in question in his September visit at the Respondent’s jobsite. . .Tr. June 975 -999, Exh. C-22. [On this point, the testimony is germane to the difference between theslow and fast modes, if not on the merits of the citation itself.] He also testified that,in that same visit, he found impulsive components of noise in all the cited machinesexcept one lathe. . .Tr. June 913, 955.RockwellThe expert Rockwell, who was called by theRespondent, was well- qualified. . .Tr. June 1027 – 1031, 1131 – 1146, Exh. R-22. Hetestified that impulse noise [which is less than 1 per second and fewer than 60 perminute] should be handled separately; and that it has been OSHA policy since 1972 toexclude or edit out such noise in testing. He also quoted an OSHA regional office andChapter 4 of the OSHA Field Manual to the same effect. . .Tr. June 1150 – 1154, 1291. Hesaid that the type of dosimeter used in the April inspection erroneously read out severaldecibels higher because of impulse noise that should have been excluded. . .Tr. June 1159,1160. He pointed out that recognized authorities took the same position. . .Tr. June 1161- 1169, Exh. R-23. He also testified about tests he had conducted in the Respondent’splant in February, 1981, using both slow and fast response dosimeters. The slow responseone [the type used in the instant case] registered 5 – 14 decibels higher than the fast. ..Tr. June 1174 – 1207, Exh. R-25 – 33. He concluded that the dosimeter overestimatesexposure in \”this\” type of environment [the Respondent’s jobsite] by 10 – 12decibels over the actual exposure level. . .Tr. June 1195 – 1202. He said that the use ofa 5dB rate of exchange dosimeter resulted in inflated exposure readings, grosslyoverestimated the true noise, and was an inaccurate instrument for impulsive or rapidlyfluctuating noise. . .Tr. June 1200 – 1202, 1209, 1234, 1236. He specified errors of 10 -15 decibels at each location that he tested. . .Tr. June 1287, Exh. R-33. It was hisopinion that the instrument used could not substantiate the allegations, and that impactnoise levels should be measured only with an impact meter or an oscilloscope. . .Tr. June1252, 1296, Exh. R-35. HolmerThe expert Holmer, who was called by the Respondent,was well-qualified. . .Tr. June 1298 – 1310, 1479 – 1481, Exh. R-36. He testified thatimpulse noise should be eliminated in determining compliance with the G-16 table. . .Tr.June 1456, 1457, 1515. He said that, because of the difference between the 3dB and the 5dBexchange rates, the Gen Rad 1954 dosimeter used in the inspection would read higher thanthe actual noise level. . .Tr. June 1447, 1455, 1466, 1467. He said that such dosimetersinvariably overestimate signals fluctuating at the rate of 1 second or less; and that nodosimeter accurately records impulse noise in the Table G-16 sense because the standardrequires a 5dB exchange rate. . .Tr. June 1441 – 1443, 1456. He also said that, althoughdosimeters read lower than theory would project, and a Gen Rad 1954 dosimeter does notoverestimate as badly as an \”ideal\” dosimeter would, it still overestimates by afactor of 10 whereas an \”ideal\” one would overestimate by 12. . .Tr. June 1467,1471.Kundert The expert, Kundert, who was called by theComplainant, was well-qualified. . .Tr. December 778 – 780, Exh. C-27, C-28. He testifiedthat the Gen Rad 1954 dosimeter was designed specifically for testing against the OSHAstandard, is excellent for that purpose, and can process short signals even though mostdosimeters cannot. Although he said it was designed to measure both continuous and impulsenoise, he acknowledged that it cannot accurately measure very short impulses but tends toproduce low readings. . .Tr. December 795 – 797, 871 – 874. Concerning the 3dB and 5dBrates of exchange, he testified that the dosimeter responds to impulsive sound as a 5dBinstrument…Tr. December 863, 864. Concerning the question of whether Table G-16 isinterpreted to include or exclude impulse sound, he testified that the OSHA field guidesays to exclude it its did ANSI S-1.25. He concluded that, if impulse noise is to beexcluded, the way to do it is by reading between the pulses, as the witness Rockwelldid…Tr. December 888 – 890. He also said that the authorities cited in Exh. R-23 did notsupport Rockwell’s position but, on the contrary, disagreed with it. . .Tr. December 798 -803. Recalled by the Complainant in rebuttal, he said that, for the type of impulsivenoise here, the sound level meter and dosimeter give almost identical results; and thathis in-court demonstration with the dosimeter anti sound level meter (measuring acontinuous sequence of impulses) produced the same results. . .Tr. 1982 March 1728 – 1730,1871 – 1876.BotsfordThe well-qualified expert, Botsford, who was calledby the Respondent, testified that the Department of Labor had recommended the exclusion ofimpact noise from Table. G-16, and impact noise was not included in Table G-16. . .Tr.December 1038 – 1040, Exh. R-66.His testimony tended to establish that impact noisecould not be accurately measured by a sound level meter but should be measured by animpact meter against a limit of 140 decibels; while continuous noise should be measuredagainst Table G-16, using a time-weighted instrument with a 5 decibel exchange rate andthen reading between the impact peaks. . .Tr. December 1076 – 1080. He said that the OSHAfield manual recommends this procedure. . .Tr. December 1077, Exh. R-76. HildyardThe Respondent, seemed to place great reliance on thetestimony of Dr. Hildyard to the effect that, although the advisory committee on OSHAstandards made a final recommendation of priority for administrative and engineeringcontrols over personal protective devices, the committee members had actually voted not toaccord priority to administrative and engineering controls over personal protectivedevices [such as ear plugs]…Tr. March 565, 583. However, even if there had been noobjection to such testimony [and the Complainant did object to it], it would be given noweight because it violates the parole evidence rule [See Evidence ?1022, 1027 of 30 Am.Jur. 2nd; sec. 77.5 of Federal Trial Handbook; and Del Prete v. Board ofSelectmen, 351 Mass. 344]. The official record of the advisory committee on OSHAstandards which said administrative and engineering controls must be tried before personalprotective equipment — governs and not evidence tending to contradict it. Accordingly, Iam limiting Dr. Hildyard’s testimony about the committee vote to whatever bearing it mayhave on the Respondent’s good faith. JonesThe expert Jones, who was called in rebuttal by theComplainant, was a well-qualified industrial noise consultant. He testified that the soundlevel meter measures noise in the slow response better than the fast and that there is nobasis for editing out impulse noise. . .Tr. 1982 March 1629 – 1639. However, he alsostated that he agreed with the statement that only steady noise is to be measured againstTable G-16. . .Tr. 1982 March 1695. Although his name also appeared on a documentapparently stating that Table G-16 values do not apply to impulse noise, he testified thatsuch use was unauthorized and did not represent his opinion. . .Tr. 1982 March 1651 -1658, 1668 – 1670. Because of his sworn testimony to that effect, I do not place anyreliability on that document as far as it concerns any opinion by him.Jones also testified that Bosford had written anarticle in which he said impulse noise should be included in measurements of industrialnoise. . .Tr. 1982 March 1637, 1638.KampermanThe expert Kamperman, who was called in rebuttal bythe Complainant, was a well-qualified industrial noise expert. He testified that thedosimeter is a very accurate Instrument for measuring noise in an industrial setting; thatit always underestimates noise; and he had found no dosimeter that read high. . .Tr. 1982March 1902, 1947, 1984. He also said that impulse noise should not be excluded frommeasurements and that industry custom is to include it in computing noise for purposes ofTable G-16. . .Tr. 1982 March 1913 – 1917. He pointed out that if impulse noises areedited out of a punching operation, there would be no noise left because they are allimpulsive signals. . .Tr. 1982 March 1898, 1911. He said that his field testing of the1954 Gen Rad dosimeter and a sound level meter produced approximately the same results,whether with or without impulse noise. . .Tr. 1982 March 1900, 1901. He also said that thefast response is not as good as the slow in determining noise per Table G-16. . .Tr. 1982March 1902. He concluded that he had never said that impulse noise should only be measuredin accordance with the 140dB peak, and had never said that impulse noise should beexcluded from measurements. . .Tr. 1982 March 1984, 1985.However, when he was asked if he had said that\”it is not possible for a simple dosimeter to correctly compute the noise dose usinga 5dB exchange rate for noises that vary in levels of less than 10 seconds,\” hisanswer included statements that \”problems come because of the OSHA 5dB exchange rate.. .because the 5dB exchange rate violates basic laws of physics\”. . . Tr. 1982 March1960-1966. He also testified that the dosimeter \”has a hard time correctly measuringanything other than steady random noise\” and that he is \”on the committee torevise standard now to make dosimeters capable of correctly measuring impulsivesound.\”. . .Tr. 1982 March 1945. He also conceded that there is \”confusion\”over the measurement of impulsive noise in the industrial environment and that he hadwritten an article stating that the standard only addresses the measurement of continuousnoise. . .Tr. 1982 March 1948, 1949, Ex. R-110. He also testified that he had made awritten statement that, for impulsive noise, \”the dosimeter will always indicate amuch higher dose that the sound level meter\” and that the disparity would be 100% ora difference of 5dB. . .Tr. 1982 March 1953, 1954, 1968, 1970. While he also testifiedthat this was an incorrect interpretation of his view, he nevertheless conceded that hehad told a seminar that \”dosimeters used in the noise environment typically found inmetal fabricating facilities would read between 5 and 13dB too high, two to six times theexpected noise dose relative to the OSHA 5 decibel exchange rate,\”. . .Tr. 1982 March1953 – 1957, 1963-1970.DISCUSSION With very minor differences, the experts all seemedto be in general agreement that impulse noise is a sound of brief duration that occursless frequently than one a second and less than 60 a minute; and includes such examples ashand clapping, dropping a book, firing a rifle, the ram of a punch press, etc. It is alsoclear that all the cited machines [with the possible exception of the lathes had impulsivecomponents in the noise. . .Tr. March 311, June 913, 921, 955, 956, 1150, 1251.As indicated above in this decision, the expertsdiffered in their opinions on the accuracy of the measurements by the dosimeter. Rockwell,Holmer, and Botsford were firm in their conclusions that the dosimeter had to beinaccurate because of the standard’s requirements that only the slow response may be used.Although Barry, Kundert, Jones and Kampermanconcluded that the dosimeter readouts were accurate, they did make many concessions[specified above] that tended to establish there were distortions by the dosimeters usedin the April inspection.In my opinion, the weight of the evidence clearlyestablishes that the dosimeters used were certain to overstate the employees’ exposure tonoise. I so find.The most troublesome question is whether impulsenoise should be included or excluded from the dosimeter readout. The standard itselfmerely uses the words \”noise\” or \”sound\” except for the word\”continuous\” in paragraph (b)(2). Table G-16, with figures going only as high as115, has a footnote: \”Exposure to impulsive or impact noise should not exceed 140dBpeak sound pressure level\”. The standard at .95(b) 1 – 3 clearly mandates that soundlevels be \”measured on the A scale. . .at slow response\”. Table G-16 alsospecifies: \”Sound Level dBA slow response\”. The Compliance Officer has nochoice: the standard must be obeyed. The dilemma is that the standard mandates the use ofthe slow response mode of testing, but the evidence establishes beyond doubt that, whenimpulsive noise is present, the slow response mode results in an inaccurate readout inexcess of the true noise level,Even if the use of the slow response dosimeterresults in distorted readings, is the question of compliance to be based on such figures?It is hard to believe that any branch of government would intend such a result. Certainlya judicial forum could not condone any decision based on inaccurate facts.The Complainant has the burden of proving that theRespondent’s employees were exposed to noise that exceeded the amounts specified in TableG-16. In my opinion, that calls for the Complainant to prove that there were actual andtrue noise levels in the amounts stated in Table G-16, and not merely readout figuresprovided by the mandated slow response dosimeter. I find that that is the Complainant’sburden of proof even if it means that the Compliance Officer has to use two sets ofinstruments: one to comply with tile mandate of the OSHA standard and a second to satisfythe demands of proof and due process of law.A third alternative, of course, is for somemodification of the standard (or Table G-16) in conformity with the most acceptabletechnology available [a need recognized by the Complainant’s very experienced expert,Barry. . .Tr. June 927]. I strongly recommend such modification because it is a scandaloussituation when the various entities concerned with safe working conditions OSHA, theemployer and employees, the Complainant and the Respondent, the attorneys, and thejudicial forum itself — are all at the mores of a system that practically guaranteescontroversy and uncertainty because even the experts themselves are in almost totaldisagreement.If the present state of the law requires the use ofinstruments in addition to any that are mandated by the standard, or calls for measures tocorrect the readout figures, or makes the Complainant’s task more difficult in any way,that is unfortunate; but the Complainant has the burden of proving its allegation.On the question of the accuracy of the slow responsedosimeter when impel – impart noise is present at the jobsite, there may be a conflict oftestimony between the experts for the Complainant and the experts for the Respondent.Assuring that all are equally honest and equally well-qualified [and 1 that them so to be]has the Complainant carried his burden of proof? I find that the dosimeter’s accuracy has not beenestablished; in fact, quite to the contrary, its inaccuracy was proven. The testimony ofthe Respondent’s experts to that effect was not shaken; and the Complainant’s experts[Barry, Jones, Kundert, and Kamperman] also made several statements tending to the sameconclusion. The inspection officer herself (Hart) also agreed that the dosimeter readoutwould be inaccurate when impulse noise was included. In that state of the evidence, I findthat the dosimeter’s accuracy was not proven. On the question of whether to include or excludeimpulse noise in determining compliance with Table G-16: I find it should be excluded. Inthe first place, its inclusion was the basic cause of the dosimeter’s inaccuracy in theinstant case. Secondly, I find that it was the customary practice for OSHA to excludeimpulse noise in determining the possibility of noise exceeding the figures in Table G-16.The uncontradicted testimony of the expert Rockwell was that it has been OSHA policy since1972 to exclude such noise; and that Chapter 4 of the OSHA Field Manual is to the sameeffect. . .Tr. June 1150 – 1154, 1291. Hart’s testimony that impulse noise was notsupposed to be included corroborates that conclusion.The Respondent has a constitutional right to betreated the same as any other employer cited under the same standard. If the customarypractice of OSHA was to exclude such impulse noise, it should have been excluded in theinstant case.Lastly, I find that any reasonable interpretation ofTable G-16 leads to the conclusion that impulse noise must be excluded. An analysis of thestandard can lead to no other conclusion. We begin with the assumption that it intended tohave a workable standard with accurate figures in Table- G-16 — and the standard shouldbe interpreted to achieve those ends. The standard clearly and explicitly states that theslow response mode must be used — but that mode cannot accurately measure impulse noise.The standard is so ambiguous about impulse noise that (in my opinion) reasonable personswould agree that two interpretations are possible: (1) that impulse noise should beincluded in the dosimeter readout; or (2) it should be excluded. The first interpretation[including impulse noise] results in an inaccurate readout. Consequently, the morereasonable conclusion is to exclude impulse noise since that is the only interpretationthat gives accurate figures in the readout while still complying with the slow responsemode, as mandated by the standard. That is the only interpretation that gives a workablestandard with accurate figures in Table G-16.In the final analysis, the Complainant has not provenits case whether impulse noise is supposed to be included or excluded. If it should havebeen excluded, that was not done here; and if it should have been included, it results inan inaccurate readout. In either event, the dosimeter used was not a reliable instrumenton which to base the citation.The difference between the true sound level and thedosimeter’s inaccurate readout was not minor but amounted to at least several decibels.When the dosimeter’s readout ranged from 94 to 101.3 decibels, an error of severaldecibels could easily bring the true figures to those in compliance with Table G-16. Whilean error of several decibels might not be of any significance if the dosimeter readoutwere greatly in excess of the figures in Table G-16, it becomes of paramount importancewhen [as here] the readout ranges from 94 to 101.3 decibels.Where the noise is so excessive that an error ofseveral decibels in the dosimeter is comparatively trivial, the inaccuracy becomesimmaterial. For example, in the Frank Nutty case [5 OSHC 1727], where the recordednoise was 8 times more than that permitted in Table G-16, the Review Commission affirmedwithout review the decision of the Administrative Law Judge that the Respondent had notcomplied with the noise standard concerned. [Although the dosimeter was held to beadequate in that case, I find it easily distinguishable from the instant case]. Here,where the alleged excessive noise is comparatively slight and the dosimeter errorcomparatively great, it must be found that the Complainant has not proven excessive noise.Offers of Proof by the ComplainantEven assuming the admissibility of the evidence inthe Complainant’s various offers of proof, the quantity and quality of evidence castingdoubt on the reliability of the dosimeter is not diminished. If the proffered evidence hadbeen admitted, it would not change my findings.Barry’s testimony of September inspectionIn seeking to establish the admissibility of Barry’stestimony concerning his September, 1980, visit to the jobsite, the Complainant offeredthe testimony of Compliance Officer Goyda that the conditions prevailing at that time weresimilar to those of the official inspection in April, 1980. The substance of Goyda’sdirect examination was that the machines and the parts produced appeared to be the same onboth dates and he observed no difference in them. . .Tr. March 29 – 31, 299 – 302. He tookno measurements but described the parts in fairly general terms. He testified that heheard the noise emitted by the machines and it was \”the same\” on both dates. ..Tr. March 303.Cochran, the Respondent’s chief engineer, testifiedthat the punch presses used some 20 – 30 different dies of varying weights, shapes, andthicknesses in producing 30 different components or parts. The weights vary from 200 toone thousand pounds in sizes ranging from 8 x 10 inches to 22 x 16 inches. . .Tr. March103 – 108, 122. He said the manner in which the machines are operated changes every day;and the number of parts and the length of the run vary with the particular job. . .Tr.March 112 – 114, 171. That is also true of the machine’s number of strokes per minute. ..Tr. March 130, 149 – 151. He testified that the parts made by machines 2208 – 2210\”are all different\” and that the two parts made on September 15th [the date ofBarry’s visit] but were \”4 absolutely different parts\”. . .Tr. March 287. Heexplained that, although the machines themselves were identical, the operation was not\”because it had a different tool in it and every tool runs differently. . .not thesame steel strip.. a different width and fed a different length.\”. . .Tr. March 289.He also pointed out that there would be \”a wide variation\” in the noise becausethe gauge of the material is \”one factor that is involved in producing noise whenthat die hits the stock\”. . .Tr. March 291, 292. He also testified that there weredifferent sounds on the lathe on some days. . .Tr. March 128.Bergeron, the Respondent’s assistant director ofmanufacturing, testified that dies may or may not be changed frequently because it is ajob shop. . .Tr. March 226 – 229.There was no contradiction of the testimony ofCochran and Bergeron on the differences in dies, parts, strokes, and length of run.Moreover, I was favorably impressed by the candor and honesty of both witnesses; and bothcertainly were in positions to know about the operations they described.It was ruled that, on the basis of Goyda’s testimonythat conditions during the April and September visits were similar, Barry’s testimonyabout his September visit was technically admissible; but both parties were alerted to thefact that it would be given very little weight. . .Tr. March 303 – 307. My opinion was[and is] that in a matter as sensitive and delicate as the determination of decibels ofnoise, more is required than Goyda’s mere eye and ear observation of the appearance andsound of machines and parts. The testimony of Barry about his September visit was admittedbecause, technically, Goyda’s testimony furnished a foundation of similarity. I have givenit very little weight because, substantively, Cochran’s uncontradicted testimonyestablished that the difference in dies, parts, strokes, and lengths of run may well haveresulted in different noise levels.REVIEW COMMISSIONIn view of my findings concerning the inaccuracy ofthe dosimeter, I have not reached items 1(b) and 1(c) of Citation #1. I purposely have notmade alternative findings because it seems to me to be of over-riding importance for theReview Commission to clear up the uncertainties arising out of the possibleinterpretations to which the standard at 29 CFR 1910.95 is susceptible. I respectfullyrequest that my decision be reviewed to that end.[As cited above. I am aware of the Frank Nuttycase interpreting a virtually identical noise standard. However, I think that decision isnot only distinguishable in several aspects from the instant case but, of greatimportance, the point raised here was not discussed there.]FINDINGS OF FACTHaving heard the testimony, observed the witnesses,and examined the exhibits, the following Findings of Fact are made:1. At all times concerned, the Respondent regularlyreceived, handled or worked with goods which had moved across state lines.2. As concerns Items #1(a) of Citation #1, thedosimeter used in the inspection did not accurately record the true sound levels.3. The true sound levels did not exceed the figuresof Table G-16.4. The sound levels exceeded those shown in TableG-16 when measured on the A scale of a standard sound level meter at slow response.CONCLUSIONS OF LAW1. At all times concerned, the Respondent was anemployer engaged in a business affecting commerce within the meaning of the Act; and theOccupational Safety & Health Review Commission has jurisdiction over the subjectmatter and the parties.2. The Complainant has not sustained the burden ofproving the Respondent violated the standard at 29 CFR 1910.95(a).ORDERThe whole record having been considered, it isordered that Citation #1, and the penalty proposed therefor, be vacated.SO ORDERED.FOSTER FURCOLOJUDGE, OSHRCDated: June 28, 1982Boston, Massachusetts\u00a0APPENDIXTHE ACTSection 654 [section 5(a)(2)] Employer \”.. .shall comply with occupational safety and health standards. . .\”Section 666 [section 17(b)] \”. ..employer who has received a citation for a serious violation. . .of this Act. . .shall beassessed a civil penalty of up to $1,000 for each such violation.\” Section 666 [section 17(k)] \”. . .aserious violation shall be deemed to exist. . .if there is a substantial probability thatdeath or serious physical harm could result. . . unless the employer did not, and couldnot. . .know of the presence of the violation.\”THE STANDARDS29 CFR 1910.95(a) – (b)(3):? 1910.95 Occupational noise exposure. \u00a0\u00a0\u00a0 (a) Protection against the effects of noise exposure shall be providedwhen the sound levels exceed those shown in Table G-16 when measured on the A scale of astandard sound level meter at slow response.\u00a0\u00a0\u00a0 (b)(1) When employees are subjected to sound exceeding thoselisted in Table G-16, feasible administrative or engineering controls shall be utilized.If such controls fail to reduce sound levels within the levels of Table G- 16, personalprotective equipment shall be provided and used to reduce sound levels within the levelsof the table.\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 (2) If the variations in noise levelinvolve maxima at intervals of 1 second or less, it is to be considered continuous.\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 (3) In all cases where the sound levelsexceed the values shown herein, a continuing, effective hearing conservation program shallbe administered.TABLE G-16 – PERMISSIBLE NOISE EXPOSURES[[1]]\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0Sound level\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0dBA slow Duration per day, hours\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0response8…………………………………………………………906…………………………………………………………924…………………………………………………………953…………………………………………………………972………………………………………………………..1001?……………………………………………………..1021………………………………………………………..105?……………………………………………………….110? or less …………………………………………….115\u00a0FOOTNOTES: [[1]] The standard is quoted in its entirely\/except for provisions dealing withdetermining noise levels by octave band analysis, a measurement technique not involved inthis case.[[2]] This problem was noted early in theCommission’s experience with the noise standard. See Weyerhaeuser Co., 74OSAHRC 57\/F4, 2 BNA OSHC 1152, 1153-54, 1974-75 CCH OSHD ? 18,468, pp. 22,485-86 (No.2116, 1974)(lead opinion); Sun Shipbuilding & Drydock Co., 74 OSAHRC 61\/A2, 2BNA OSHC 1181, 1182-83, 1974-75 CCH OSHD ? 18,537 (No. 268, 1974) (lead and concurringopinions); Weyerhaeser Co., 77 OSAHRC 9\/A2, 4 BNA OSHC 1972, 1974-75, 1976-77 CCHOSHD ? 21,465, pp. 25,748-49 (No. 1231, 1977), aff’d in pertinent part, subnom. Noblecraft Industries, Inc. v.Secretary, 614 F.2d 199 (9th Cir. 1980).[[3]] Collier-Keyworth argues that the use of adosimeter is inherently inconsistent with the standard, which specifies that noise levelsare to be measured with a standard sound level meter. As we have explained, the dosimeteritself contains the circuitry of a standard sound level meter. It also contains othercircuitry, but the other circuitry only performs automatically calculations that wouldotherwise have to be done manually. Thus, the dosimeter does precisely what the standardrequires: measures sound levels with a standard sound level meter and performs thecalculations required by the cumulation formula. Whether it performs these functions withsufficient accuracy is another question, which we will address later. For now, we noteonly that the use of a dosimeter is consistent with the standard, and rejectCollier-Keyworth’s contrary argument Love Box Co., 76 OSAHRC 45\/D5, 4 BNA OSHC1138, 1140 n. 2 1975 76 CCH OSHD ? 20,588, p. 24,628 & n. 2 (No. 6286, 1976).[[4]] In 1981, section 1910.95(b)(3) was replacedwith a new standard, known as the \”hearing conservation standard\” or\”hearing conservation amendment,\” which lists in detail the requirements ahearing conservation program must have. 46 Fed. Reg. 4078 (Jan. 16, 1981), now codified at29 C.F.R. ? 1910.95(c)-(p). The hearing conservation standard requires an employer toimplement a hearing conservation program whenever employee noise exposures equal or exceedan eight-hour time-weighted average level of 85 dBA. 29 C.F.R. ? 1910.95(c)(1). It alsoprovides that, in determining whether this limit is exceeded, \”[a]ll continuous,intermittent and impulsive sound levels from 80 decibels to 130 decibels shall beintegrated into the noise measurements.\” 29 C.F.R. ? 1910.95(d)(2)(i). Thus, impulsenoise is explicitly included in the hearing conservation standard. However, inpromulgating the hearing conservation standard, the Secretary did not purport to amend anyprovision of the old standard except subsection (b)(3). The hearing conservation standardtherefore does not affect whether impulse noise is included under the standard involved inthis case, section 1910.95 (a)-(b)(2), which require administrative and engineering noisecontrols and personal protective equipment.[[5]] The Secretary’s expert witness, Dr. BurtonJaffe, testified that noise is a \”mechanical transfer of energy that really shakesthe hair cells and damages them.\” The manner in which this testimony is summarized inthe Secretary’s brief echoes what has become known as the \”equal energy rule,\” atheory that equal amounts of noise and energy are equally harmful regardless of their formor duration. This theory was discussed at length in the preamble to the Secretary’s newhearing conservation standard and expressly applied to impulse noise. See 46 Fed. Reg. at4096. Its application to impulse noise seems to have been upheld on the basis of therulemaking record compiled by OSHA to support the hearing conservation standard. SeeForging Industry Ass’n v. Secretary of Labor, 773 F.2d 1436, 1451 (4th Cir. 1985) (enbanc).[[6]] The Secretary attempts on the basis of awitness’s testimony to reconcile Table G-16 with the 140 dB provision. We shall considerthis testimony after we have completed our review of the text of the standard. See note 12below.[[7]] When the original version of the standard waspublished by the Labor Department’s Bureau of Labor Standards under the Walsh-HealeyGovernment Contracts Act, 41 U.S.C. ? 35-45, this provision was set in the same size typeas other text and placed after the footnote to the table. See 34 Fed. Reg. 7949 (1969) and35 Fed. Reg. 1015 (1970) (corrections to standard). When the standard was adopted andreprinted under the OSH Act in 1971, the Secretary did not purport to–and was in anyevent not empowered to–make any substantive change in it. Yet, the 140 dB provision wasthen printed in the same small type as the footnote to the table, apparently because atypesetter mistook it to be a continuation of the footnote to the table immediately above.36 Fed. Reg. 10466, 10518 (1971). We are confirmed in this impression by four LaborDepartment documents. The Labor Department’s own edition of OSHA standards, I GeneralIndustry Standards and interpretations 144 (OSHA No. 2077, 1984), prints the 140 dBimpulse noise provision in, and in the same size type as, the text. The 140 db provisionis still part of the text of the original Walsh-Healey standard, 41 C.F.R. ? 50-204.10. ALabor Department bulletin interpreting the Walsh-Healey standard characterized theprovision as \”[t]he last sentence in paragraph (d) of section 50-204.10. . . .\”Bureau of Labor Standards, U.S. Dept. of Labor, Bulletin 334, Guidelines to TheDepartment of Labor’s Occupational Noise Standards for Federal Supply Contracts, 4(Dec. 4, 1970). Finally, the corresponding provision in OSHA’s noise standard for theconstruction industry–which was adopted at about the same time as the original generalindustry standard (see 36 Fed. Reg. 7340, 7348 (1971))–was printed in a separatesubsection, now codified as 29 C.F.R. ? 1926.52(e).[[8]] That provision states in part that \”[w]henan agency decision rests on official notice of a material fact not appearing in theevidence of the record, a party is entitled, on timely request, to an opportunity to showthe contrary.\”[[9]] The record contains various terms used todescribe non-impulsive noise, such as steady noise, continuous noise, steady-state noise,and intermittent noise. Except for intermittent noise, these terms suggest noise that isconstant in intensity over a relatively long period of time. Intermittent noise varies inintensity, but not as rapidly as impulse noise. For example, noise from a machine that isalternately on and off for several seconds at a time would be classified as intermittentnoise.[[10]] Even in 1981, when the Secretary promulgatedthe hearing conservation amendment to the noise standard, there was a relative dearth ofinformation on impulse noise. The Secretary noted: \”In contrast to the studies ofcontinuous noise mentioned above, dose-response relationships for impulse noise are not soeasily defined.\” 46 Fed. Reg. at 4096.[[11]] ACGIH, \”Threshold Limit Values ofPhysical Agents\” (1969), reprinted in National Safety Council, Fundamentalsof Industrial Hygiene, Appendix A, pp. 739-41 (1971). Collier-Keyworth introduced asExhibit R-101 the 1971 version of the ACGIH standard, which appears to be identical.[[12]] See also a chapter by Jones, \”Standardsand Threshold Limit Values for Noises,\” in National Safety Council, IndustrialNoise and Hearing Conservation ch. 11, p. 309 (Olishifski & Harford eds.1975)(ACGIH limits \”incorporated in\” Walsh-Healey standard). That the ACGIHstandard substantially influenced the drafter of the Walsh-Healey standard leads theSecretary to rely heavily on testimony by Jones, who was chairman of the ACGIH committee,that the table in the ACGIH standard corresponding to Table G-16 \”would includeanything that the sound level meter would respond to, be it a continuous[,] impact [or]impulsive noise.\” Jones further testified that the 140 dB impulse noise provision wasintended to be an additional restriction on impulse noise, included because of thepossibility that high intensity impulses could be harmful even if the limits in the tablewere not exceeded. The Secretary states that Jones \”was, in effect, the author of the[140 dB impulse noise] provision\” because the limits in the table adopted by Jones’sACGIH Committee were \”issued in virtually identical form by the Department of Laboras a standard under the Wash-Healey Act. . . .\” We are unable to credit this part ofJones’s testimony because the ACGIH standard expressly stated that the exposure limits inits table do not apply to impulse noise. We therefore disagree with the argument inthe Secretary’s brief that this part of Jones’s testimony is a reliable guide to theintent of the drafters of the Walsh-Healey standard.[[13]] The bulletin was revised on June 8, 1971,after the Walsh-Healey standard was adopted under the OSH Act. The 1971 version wasintroduced into evidence.[[14]] A passage written by Dr. Van Atta in IndustrialNoise and Hearing Conservation, n. 12 above, at 322, also suggests this. The passage,which was read into the record, states:This regulation provides for a basic level of 90 dBAfor continuous noise exposure with a tradeoff of 5 dBA for each halving of thenoise exposure time. This includes a rough allowance for interruptions of noise exposure.Impact noises must be limited to less than 140 dB peak sound pressure level.It is important to note that this is a doublerequirement. For example, in a power-press department, it is necessary that both theinstantaneous peaks of the impact noises arising out of the operation of large presses bebelow 140 dB and that the continuous ambient background noise be below 90 dBA.[Emphasis added.][[15]] J. Barry, \”Problems in Enforcement of theOccupational Noise Standard,\” in Proceedings of Noise-Con 79, Machinery NoiseControl, 11 (Sullivan & Crocker eds. 1979). At the hearing in this case, Dr. Barryfirst testified that Table G-16 \”has no relation to impulse noise.\” He laterstated, however, that the standard did intend for impulse noise to be included in dosagecalculations.[[16]] The chapter is printed in Occup. Safety andHealth Admin., U.S. Dep’t of Labor, VI OSHA No. 3058, Industrial Hygiene FieldOperations Manual (1980), and in CCH Employ. S. & H. Guide, Edition No. 419 (May24, 1979).[[17]] At the hearing in this case, Dr. Barry statedthat he recommended the use of fast response in this instruction to enable the inspectorto analyze the components of the noise to assist in evaluating the feasibility ofengineering controls. (Fast response, like slow response, is a setting on a sound levelmeter. For the moment it is enough to observe that where impulse noises are closelyspaced, fast response is more accurate than slow response in displaying the truebackground noise level.) When the Secretary promulgated the hearing conservation amendmentin 1981, he said that this IHFOM provision \”is clearly at variance with the presentstandard and is being deleted.\” 46 Fed. Reg. 4078, 4137 & n. 11(Jan. 16, 1981).If, as Dr. Barry stated, the purpose of the provision was to assist inspectors to evaluatethe feasibility of engineering controls, there would have been no need for the Secretaryto disavow it in this manner. In sum, we read the instruction as OSHA did–to signify thatimpulse noise was not to be included in determining whether employee exposure exceedsTable G-16 levels.The Secretary also claims that the prescription ofslow response in the standard is inconsistent with any intent to exclude impulse noisefrom Table G-16. We are unconvinced of any logical inconsistency here. The ACGIHstandard–from which the Secretary acknowledges the drafters of the Walsh-Healeystandard–from which the Secretary acknowledges the drafters of the Walsh-Healey standarddrew heavily–both prescribed slow reposes and excluded impulse noise. The same is true ofthe noise standard proposed by the Secretary in 1974. See 39 Fed. Reg. 37773, 37775 (Oct.24, 1974), proposing new section 1910.95(c)(1)(ii).[[18]] Turner involved three presses in thesame room. One stroked at a rate of 27 per minute, and a second at 33 to 38 strokes perminute. 4 BNA OSHC at 1556, 1976-77 CCH OSHD at pp. 25,273-4. Thus, these two pressesalone would produce 60 or more noise impulses per minute, i.e., continuous noise.[[19]] Collier-Keyworth occasionally alludes to thispoint in a confusing fashion, speaking of dosimeters having an \”effective\”exchange rate of 3 decibels. A dosimeter set to employ a 3 decibel exchange rate wouldregister the same sound levels as would one set to employ a 5 decibel exchange rate. Itwould record a higher dosage, however, because the lower exchange rate shortenspermissible durations. Yet, Collier-Keyworth does not argue that OSHA set its dosimetershere to employ a 3 decibel exchange rate. Instead, it maintains, based on the testimony ofexpert witnesses, that in impulsive noise environments dosimeters set to use a 5 decibelexchange rate and slow response will so overcount \”true noise levels\” as toapproximate the results of employing a 3 decibel exchange rate with fast response.Collier-Keyworth’s argument rests on the assumption that under Table G-16 sound levelsmust be measured with a fast response instrument. We will discuss the validity of thisassumption in the text below.[[20]] This effect is illustrated by Ex. R-26, whichcontains several strip chart recordings made by Rockwell, and by C-22L, a strip chartrecording made by Barry. One recording in Ex. R-26 shows noise patterns for a power pressoperating at 100 strokes per minute. Because the peaks are less than one second apart, thenoise is quasi-continuous. With the sound level meter set for fast response, whichcorresponds to an integration time of an eighth of a second, the individual impulses arereadily visible and have peak intensities of 108-109 dBA superimposed on a background ofabout 99 dBA. On slow response, however, the noise appears relatively continuous at alevel of 104-105 dBA. Thus, compared to fast response, the sound level meter at slowresponse reads higher troughs but lower peaks, that is, the individual impulses appear tobe of longer duration but lower peak intensity. The reason for the difference is best explained bydiscussing the behavior of the needle of a sound level meter: At slow response, the needledoes not have time to return to the continuous, background noise level before the nextimpulse comes along and causes it to swing back up. For example, in Ex. C-22, the soundpeaks are about two to three seconds apart, and hence much farther apart than in Ex. R-26. The noise levels indicated by slow response are still different from that of fastresponse but not as different as in Ex. R-26, where noise peaks only six-tenths of asecond apart gave the needle little time to swing back before the next impulse arrives.[[21] ]Its argument is echoed in the observation ofone dosimeter manufacturer that \”[i]t is the requirement of a slow response timeconstant in a dosimeter that causes a dosimeter to appear to read high.\” Ex. R-24,statement by Quest Electronics.[[22]] See American Mining Congress v.Marshall, 671 F.2d 1251, 1255-7 (10th Cir. 1982) (discussing whether measuring methodprescribed by mine health regulation is \”arbitrary, capricious, or an abuse ofdiscretion\” within the meaning of the Administrative Procedure Act).[[23]] The brief at the Chocolate ManufacturersAssociation, which the Commission permitted to appear on review as an amicus curiae,argues that dosimeters generally are unreliable. Attached to its brief are studies by Dr.Paul Hess of Hershey Foods that argue in support of this thesis and that criticize OSHA’sevaluation of Dr. Hess’s studies in OSHA’s preamble to revisions in 1983 of the hearingconservation standard. The Chocolate Manufacturers Association also asks the Commission totake official notice of statements in OSHA’s Industrial Hygiene Technical Manual,p. B-47 (March 30, 1984) (\”the IHTM), reprinted in CCH Employ. S. & H.Guide, Extra Edition No. 680 (May 24, 1984), and in 2 BNA Occup. S. & H.Rep. 77:8001, 77:8925 (June 14, 1984). The Secretary of Labor objects to the ChocolateManufacturers Association’s brief, arguing that it improperly introduces evidence. Wedeferred ruling on this motion and on the taking of official notice of the IHTM material.We take official notice of the lHTM but we are notpersuaded that accepting its statements as true mandates a result here. The portion of theIHTM relied on by the Chocolate Manufacturers Association warns OSHA field personnel that\”[s]hort-duration pulses with a low repetition rate may be completely eliminated fromthe dosimeter readings simply because the averaging circuits in the instruments cannotrespond fast enough to the change in level.\” However, we understand this passage tomean that dosimeters sometimes undercount the noise level when certain impulses arepresent; moreover, if \”low repetition rate\” refers to impulses more than onesecond apart, then the supposed inaccuracy is irrelevant because we hold that suchimpulses may not be counted at all. Another passage relied on by the amicus states that\”[c]onversely, pulses with a higher repetition rate may be overestimated by thedosimeter because the averaging circuits will build up to the high level but will not havetime to drop back down between pulses.\” We are puzzled by this passage, for it couldbe read to complain of the slow response mode mandated by OSHA’s own standard. In anyevent, if it refers to impulses more than one second apart, it is irrelevant for thereasons we have already stated. And if it refers to impulses less than one second apartthen it is also irrelevant because under subsection (b)(2), the dosimeter does not have todrop back down between impulses at all. Thus, we are not persuaded that the IHTM requiresrejection of the dosimeter readings here.On the other hand, we grant the Secretary’s motion tostrike those portions of the Chocolate Manufacturers Association brief that introduces thestudies of Dr. Hess. We decline to take official notice of this material. The materialattached by the amicus to its review brief is largely evidentiary, consisting of papersand studies by Dr. Hess challenging the accuracy of dosimeters generally. As the Secretaryargues, however, the author of this material has not been subjected to cross- examinationand the Secretary’s counsel has had no opportunity to evaluate, impeach or rebut hisstudies. Thus, if this new material were to be considered, a remand to Judge Furcolo wouldbe in order. Yet, this reopening of the record would be on the implied invitation of anamicus, not a party. In these circumstances, we adhere to our rule against the admissionof evidentiary material in review briefs. E.g., Anoplate Corp., 86 OSAHRC____, 12 BNA OSHC 1628, 1683 n. 6, 1986 CCH OSHD ? 27,519, pp. 35,681-2 n. 6 (No.80-4109, 1986).[[24]] Collier-Keyworth points out that oncross-examination Hart testified she did not know the \”strokes per minute\” forthe presses and suggests that this casts doubt on her testimony that she measured thespeed of the presses. However, Hart’s testimony that she did not know the \”strokesper minute\” does not contradict her unequivocal testimony that she timed the pressesand found that the time between strokes was less than one second. Under the standard, thenoise is deemed continuous if the time between strokes is less than one second and, oncethis is known, it is not necessary to determine the exact time between strokes or theexact stroke rate.[[25]] The strip chart recordings of noise levelsmade by Barry and Rockwell show noise levels in the vicinity of the presses ranging from95 to 105 dBA. Although these measurements were made on different days than Hart’s, theylend credence to Hart’s measurements indicating that the sound levels near the presseswere typically in this range.[[26]] See Table 2 of Field Service Memorandum No.11, in Appendix B, p. B-36 of the IHTM, note 23 above, Cf. 29 C.F.R. ?1910.95, Appendix A, Table A-1 (hearing conservation amendment) (entry for 91.9 dBAcorresponds to dose of 130 percent).[[27]] The error factors for Type 2 sound levelmeters are found in ANSI S1.4-1971, \”Specification for Sound Level Meters,\” at11, Table 3. Some of the information in that table, including the error factor at 8000hertz, was included in the paper Dr. Barry presented at Purdue University, which appearsin the record as Exhibit R-62. OSHA applied that information to Type 2 dosimeters in itsIHTM. See Table 1 of Field Service Memorandum No. 12, in Appendix B, pp. B-44–B-45of the IHTM, note 23 above.[[28]] Because he vacated all citation items onfinding that the standard excluded impulse noise, Judge Furcolo did not make findings onthe merit. Normally, we would remand to him for such findings. However, in view of the ageof the case, we will make our own findings.[[29]] The Secretary did not attempt to show thatadministrative controls for these machines were feasible.[[30]] Barry believed that erecting acousticalenclosures entirely around the presses would be impractical due to space limitations andproduction demands.[[31]] The dies for each press were changed anaverage of about once per day. Some of Collier-Keyworth’s dies weighed as much as 1,000pounds and had to be changed using a chain hoist. When the chain hoist was used, the diecould swing into the enclosure and damage it. Barry testified that this could be avoidedif the operator was careful. Holmer testified, however, that another company experiencedsevere damage to similar enclosure after 14 to 20 die changes. Holmer also estimated thatenclosures would add 20 to 40 minutes to the time required for a die change.[[32]] The highest dosimeter reading the Secretaryobtained for any of the press operators was 305%. This is equivalent to an eight-hourtime-weighted average exposure of 98 dBA. See section 1910.95, Appendix A, Table A-1.[[33]] Most of the studies relied on in the paperwere performed with gunshot noise, but the authors considered the information sufficientlygeneral to be extended to other types of impulse noise.[[34]] Threshold shift is a measure of hearing loss.A person’s hearing threshold is the lowest sound level in decibels that person can detect.If the person suffers hearing loss, his threshold increases, i.e., he can no longer heardecibel levels as low as he previously could. The number of decibels by which histhreshold increases is his threshold shift. A permanent hearing loss is referred to as apermanent threshold shift or PTS. Short exposures to high noise levels can cause atemporary hearing loss, or temporary threshold shift. When a person suffers a temporarythreshold shift, his hearing recovers after the exposure to high noise levels ceases.However, repeated exposures sufficient to cause temporary threshold shifts can lead to apermanent threshold shift. Therefore, to test whether noise exposures give rise to thepossibility of permanent hearing loss, scientists measure temporary threshold shifts inexposed individuals. If an exposure produces measurable temporary threshold shifts,repetitive exposures of the same magnitude will eventually cause permanent thresholdshifts. See 46 Fed. Reg. 4078, 4080 (1981)(preamble to hearing conservation amendment).”