Product Noise Labeling Hearing Protection Devices, 39150-39196 [E9-18003]

Agencies

• ENVIRONMENTAL PROTECTION AGENCY

[Federal Register Volume 74, Number 149 (Wednesday, August 5, 2009)]
[Proposed Rules]
[Pages 39150-39196]
From the Federal Register Online via the Government Printing Office [www.gpo.gov]
[FR Doc No: E9-18003]



[[Page 39149]]

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Part II





Environmental Protection Agency





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40 CFR Part 211



Product Noise Labeling Hearing Protection Devices; Proposed Rule

Federal Register / Vol. 74, No. 149 / Wednesday, August 5, 2009 / 
Proposed Rules

[[Page 39150]]


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ENVIRONMENTAL PROTECTION AGENCY

40 CFR Part 211

[EPA-HQ-OAR-2003-0024; FRL-8934-9]
RIN 2060-A025


Product Noise Labeling Hearing Protection Devices

AGENCY: Environmental Protection Agency (EPA).

ACTION: Proposed rule.

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SUMMARY: By this action the Environmental Protection Agency proposes to 
revise the Noise Labeling Standards for Hearing Protection Devices 
(HPD). These standards have not been amended since 1979 and 
technologies have evolved and improved in the interim. The proposed 
revisions provide manufacturers with newly developed testing 
methodologies that are the most appropriate to assess and label hearing 
protection devices, and to allow legitimate hearing protection products 
to be sold as such in U.S. markets. In particular, this action should 
result in the availability of a new generation of significantly 
improved devices that are precluded from entering the marketplace as 
``hearing protectors'' by the 1979 regulation. Finally, the Agency is 
mindful of the relatively large percentage of small entities that 
comprise the HPD industry. In recognition of the evolutionary changes 
in marketing and selling products brought about by the internet, and in 
order to minimize the potential economic burden on manufacturers that 
sell their products ``exclusively'' over the internet, the Agency is 
proposing to allow ``electronic labeling'' as a means for certain 
manufacturers (as defined in subpart B) to comply with the labeling 
requirements of this proposed rule.

DATES: Comments. Written comments must be received on or before 
September 4, 2009.
    Public Hearing. If requested by August 17, 2009 the EPA will hold a 
public hearing on August 25, 2009. If a public hearing is held, anyone 
that would like to speak at the hearing should notify the EPA by August 
18, 2009.

ADDRESSES: Submit your comments, identified by docket ID number EPA-HQ-
OAR-2003-0024, by one of the following methods:
     www.regulations.gov: Follow the on-line instructions for 
submitting comments.
     E-mail: a-and-r-docket@epa.gov.
     Fax: (202) 566-1741.
     Mail: EPA Labeling Regulation, Docket Number EPA-HQ-OAR-
2003-0024, Environmental Protection Agency, EPA Docket Center, Mailcode 
6102T, 1200 Pennsylvania Ave., NW., Washington, DC 20460.
     Hand Delivery: EPA Docket Center, Public Reading Room, EPA 
West, Room 3334, 1301 Constitution Ave., NW., Washington, DC 20460. 
Such deliveries are only accepted during the Docket's normal hours of 
operation (Monday through Friday, from 8:30 a.m. to 4:30 p.m.), 
excluding legal holidays and special arrangement should be made for 
deliveries of boxed information. The telephone number for the Public 
Reading Room is (202) 566-1744, and the telephone number for the Air 
Docket is (202) 566-1742.
    Instructions: Direct your comments to Docket ID Number EPA-HQ-OAR-
2003-0024. EPA's policy is that all comments received will be included 
in the public docket without change and may be made available online at 
www.regulations.gov, including any personal information provided, 
unless the comment includes information claimed to be Confidential 
Business Information (CBI) or other information whose disclosure is 
restricted by statute. Do not submit information that you consider to 
be CBI or otherwise protected through www.regulations.gov or e-mail. 
The www.regulations.gov Web site is an ``anonymous access'' system, 
which means EPA will not know your identity or contact information 
unless you provide it in the body of your comment. If you send an e-
mail comment directly to EPA without going through www.regulations.gov, 
your e-mail address will be automatically captured and included as part 
of the comment that is placed in the public docket and made available 
on the Internet. If you submit an electronic comment, EPA recommends 
that you include your name or other content information in the body of 
your comment and with any disk or CD-ROM you submit. If EPA cannot read 
your comment due to technical difficulties and cannot contact you for 
clarification, EPA may not be able to consider your comment. Electronic 
files should avoid the use of special characters, any form of 
encryption, and be free of any defect or viruses. For additional 
information about EPA's public docket, visit the EPA Docket Center 
homepage at https://www.epa.gov/epahome/dockets.htm.
    Docket: All documents in the docket are listed in the 
www.regulations.gov index. Although listed in the index, some 
information is not publicly available, e.g., confidential business 
information (CBI) or other information whose disclosure is restricted 
by statute. Certain other material, such as copyrighted material, will 
be publicly available only in hard copy. Publicly available docket 
materials are available either electronically in www.regulations.gov or 
in hard copy at the EPA Air Docket, EPA/DC, EPA West, Room 3334, 1301 
Constitution Ave., NW., Washington, DC. The Public Reading Room is open 
from 8:30 a.m. to 4:30 p.m., Monday through Friday, excluding legal 
holidays. The telephone number for the Public Reading Room is (202) 
566-1744, and the telephone number for the Air Docket is (202) 566-
1742.

FOR FURTHER INFORMATION CONTACT: Ms. Catrice Jefferson, U.S. 
Environmental Protection Agency, Office of Air and Radiation, Mail Code 
6103A, 1200 Pennsylvania Avenue, NW., Washington, DC 20460. Telephone 
Number--(202) 564-1668; Fax Number--(202) 564-1554; and E-mail 
Address_jefferson.catrice@epa.gov.

SUPPLEMENTARY INFORMATION: Outline. The information presented in this 
preamble is organized as follows:

I. Noise Control Act Authorities
II. Introduction
III. Background
IV. Product Applicability
V. Incorporation by Reference
VI. Test Methodologies
VII. Noise Reduction Rating Strategies
VIII. Label Format and Content
IX. Compliance Requirements
X. Cost Impact Analysis
XI. Statutory and Executive Order Reviews

I. Noise Control Act Authorities

    In the Noise Control Act of 1972 (42 U.S.C. 4907), hereinafter 
``the Act'', the Congress declared that it is the ``policy of the 
United States to promote an environment for all Americans free from 
noise that jeopardizes their health and welfare.'' Congress further 
declared that one purpose of this Act is ``* * * to authorize the 
establishment of Federal noise emission standards for products 
distributed in commerce, and to provide information to the public 
respecting the noise emission and noise reduction characteristics of 
such products.''
    Section 8 (Labeling) of the Act states that ``the Administrator (of 
the Environmental Protection Agency) shall, by regulation, designate 
any product (or class thereof)--(1) which emits noise capable of 
adversely affecting the public health or welfare; or (2) which is sold 
wholly or in part on the basis of its effectiveness in reducing 
noise.'' Further, of direct relevance to this proposal, it provides 
that ``the Administrator shall by regulation require that notice be 
given to the

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prospective user of the level of the noise the product emits, or of its 
effectiveness in reducing noise, as the case may be. Such regulations 
shall specify (1) whether such notice shall be affixed to the product 
or to the outside of its container, or to both, at the time of its sale 
to the ultimate purchaser or whether such notice shall be given to the 
prospective user in some other manner, (2) the form of the notice, and 
(3) the methods and units of measurement to be used'' [in developing 
the required information notice].''

II. Introduction

    EPA has issued rules, found at 40 CFR Part 211, subpart B, which 
implement section 8 of the Act. EPA issued these rules in 1979 (44 FR 
56120). These rules require manufacturers of hearing protection devices 
(HPD), that are entered into commerce in the United States, to provide 
the prospective user with information regarding the products' 
effectiveness in reducing the level of noise (unwanted sound) entering 
a user's ears. The regulation requires that such information be 
presented at the time of its sale to the ultimate purchaser on a 
label(s) that is readily visible at the point of purchase or 
distribution to users.
    Since 1979, the demand for hearing protector devices has increased 
dramatically due, in part, to an increased awareness of hearing loss in 
the workplace and the increased stringency of occupation and health 
regulations at the federal and state levels. The Agency estimates the 
current legal hearing protector market to be approximately four (4) 
billion units annually, comprised of about 2.1 billion units sold to 
industrial users and an estimated 1.9 billion sold to military and 
commercial users.
    As a result of an increased demand for more effective products, 
significant technological changes have occurred in the design, 
performance and comfort of hearing protectors with the resultant 
introduction of new products that, unfortunately, are not amenable to 
the current regulatory testing and rating schemes. These products 
include special purpose ``passive'' (non-electronic aided) devices, 
custom molded and tuned devices, electronic noise reduction devices, 
sound restoration devices and combination hearing protector 
(communication headset). Other changes that have occurred in the 
hearing protector industry include the consolidation of U.S. and 
foreign manufacturers, and an increasing number of foreign-made 
products finding their way into U.S. commerce that are not in 
compliance with the existing rule.
    Today's proposal reflects these technological advances and 
specifies the new and revised test methods to determine product 
effectiveness; the mathematical process to determine a numeric 
effectiveness rating(s) (i.e., Noise Reduction Rating (NRR)); the 
required graphic and textual information for the required labels; the 
introduction of electronic labeling for organizations that sell their 
hearing protectors exclusively via the internet; and future compliance 
testing to assure the continuous accuracy of product effectiveness and 
label information. EPA's overall objectives remain, as they were 30 
years ago:
    (1) Provide accurate and understandable information to hearing 
protector purchasers, users, and hearing conservation professionals 
regarding the acoustic performance of hearing protection products in 
specific noise environments so that meaningful product comparisons, 
with respect to the reduction of sound entering a user's ears, can be 
made as part of a product purchase or use decision.
    (2) Provide such information with minimal Federal involvement by 
ensuring the labeling requirements are structured to minimize 
administrative, economic, and technical impacts on manufacturers, 
distributors, and other interested parties.
    (3) Promote improvements in hearing protector design, performance, 
and user acceptability.
    (4) Promote public awareness of potential damage to hearing that 
can result from unprotected exposure to high intensity sound.

III. Background

    Since EPA's promulgation of the 1979 regulation, the federal 
government, universities and industry have conducted research on the 
effectiveness of hearing protection devices when used in ``real world'' 
settings. Professional and trade organizations, manufacturers and other 
federal agencies have presented their concerns to the EPA on a number 
of significant issues including the currently required test method, the 
required Noise Reduction Rating (NRR), and the required textual 
information on labels. All interested parties generally agree that the 
existing regulation needs to be revised to address new technology 
products, related test methodologies, and current user needs.
    In response, EPA gave notice via the Agency's Web site and by 
written invitation to interested parties to participate in a workshop 
at EPA headquarters in Washington, DC on March 27-28, 2003. The EPA 
sought detailed technical concerns, new information and recommendations 
relevant to the current federal labeling requirements for hearing 
protection devices, with particular emphasis in the following areas:

(1) Product Label

     Primary label information and format
     Supporting information
     Label size and placement

(2) New Hearing Protector Technologies

     Sound restoration systems
     Active and passive devices
     Active noise reduction
     Communication headset

(3) Noise Reduction Effectiveness Rating

     Test methodologies
     Passive and active devices
     Effectiveness metric
     Periodic retesting of products
    The two-day workshop included presentations of invited papers that 
provided the historic basis for the current hearing protector 
regulation; a review of technical revisions to test methods since the 
1979 promulgation of the regulation; an analysis of the relationship of 
the current Noise Reduction Rating (NRR) to current American National 
Standards Institute (ANSI) and International Standards Organization 
(ISO) test protocols; and an overview of new hearing protector 
technologies.
    The workshop also included ``break-out'' sessions to address the 
three major topic areas noted above. The sessions were facilitated by 
personnel from the National Institute for Safety and Health (NIOSH), 
and conducted informally without transcript to stimulate the free flow 
of ideas and exchange of information. However, the session facilitators 
recorded the essence of the discussions, while preserving the autonomy 
of the commenters.
    All formal presentations are available in EPA Docket Number EPA-HQ-
OAR-2003-0024. The docket also contains summaries of each of the 
breakout sessions and an overall summary that integrates the 
conclusions and recommendations of the sessions. The proceedings of the 
workshop, including all presentations and summaries, will be referred 
to henceforth as ``the report'' or ``the workshop report.'' The report 
may be found at document number twenty-nine (29) in the above 
referenced docket.
    The workshop presented a number of reasons why the existing 
regulation should be revised. The most notable are summarized below:

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A. Product Applicability

    The Agency has been aware of electronic devices such as active 
noise cancellation, sound restoration, combination communication 
protectors, that were essentially barred from claiming the acoustic 
noise reduction benefits attendant to these devices due to the 
limitations of the federal test procedures designed for non-electronic 
hearing protectors. Similarly, some protectors that rely upon 
acoustical and mechanical behavior to increase attenuation were also 
barred. This is because absent an appropriate measure of the product's 
noise reduction effectiveness, it cannot be sold as a hearing 
protection device.

B. Noise Reduction Rating

    The most-expressed concern was with the currently-required noise 
reduction rating (NRR) metric the single-number rating scheme that EPA 
specified to quantitatively rate the effectiveness (i.e., the sound 
attenuation or sound reduction) offered by a hearing protection device 
when used as instructed by its manufacturer. In particular, it was 
alleged that most purchasers and users of hearing protectors have a 
limited understanding of the NRR, believing that the higher the 
numerical rating, the better the product. While technically correct, it 
was suggested that purchasers or users may select products primarily on 
the basis of NRR differences as small as 1 decibel (dB), whereas issues 
of comfort, compatibility with safety equipment, communication needs, 
and ease of use can be of equal or greater importance to the ultimate 
user.
    Field studies by various researchers,\1\ over the past three 
decades, revealed a relatively poor correlation between the labeled NRR 
of selected protectors, as determined from testing in accordance with 
the American National Standards Institute (ANSI) S3.19-1974 test 
procedure, and the attenuation realized by typical users of these 
protectors when tested without the benefit of the experimenter fitting 
the device as required in ANSI S3.19. This difference was more 
pronounced with earplugs than with earmuffs, where the former device 
requires specific fitting skills by the user.
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    \1\ The referenced studies can be found in the Federal Docket at 
https://www.regulations.gov, docket number EPA-HQ-OAR-2003-0024.
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    Based in large part on these referenced field studies, one Federal 
agency has made significant modifications to their criteria governing 
the application of the NRR for determining acceptable employee noise 
exposure in the work place. The Department of Labor/Occupational Safety 
and Health Administration (OSHA) has instructed its inspectors to 
``derate'' (reduce) a hearing protector's estimated attenuation by 50 
percent when assessing the relative effectiveness of hearing protectors 
in lieu of engineering noise reduction controls.\2\
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    \2\ Occupational Safety and Health Administration (1999). OSHA 
Technical Manual, Section IV, Appendix IV:C, Methods for Estimating 
Hearing Protector Attenuation. Washington DC: Office of Science and 
Technology assessment https://www.osha.gov/dts/osta/otm/noise/hcp/attenuation_estimation.html.
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    The National Institute for Occupational Safety and Health (NIOSH) 
also suggests the derating of protectors in the workplace. However, in 
contrast to OSHA, they suggest subtracting differing percentages from 
the labeled NRR for each of the three types of hearing protectors: 25% 
from the labeled NRR of earmuffs, 50% from the labeled NRR of foam 
earplugs, and 70% from the NRR of all other earplugs.\3\
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    \3\ National Institute for Occupational Safety and Health 
(1998). Occupational Noise Exposure, Revised Criteria, 1998. 
Publication No. 98-126. Cincinnati, OH: U.S. Department of Health 
and Human Services, Public Health Service, Centers for Disease 
Control and Prevention, National Institute for Occupational Safety 
and Health.
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    In both cases the recommended ``derating'' is based on the 
agencies' engineering judgment and not controlled scientific 
determination and consequently could lead to unintended consequence of 
``over protection'' that could obscure warning signals or necessary 
voice communication.

C. Test Methodology

    The American National Standards Institute has withdrawn the S3.19-
1974 performance test standard (``Method for the Measurement of Real-
Ear Protection of Hearing Protectors and Physical Attenuation of 
Earmuffs''), which is mandated in the current regulation (40 CFR 211 
subpart B) and replaced it with ANSI/ASA S12.6-2008, ``Methods for 
Measuring the Real-Ear Attenuation of Hearing Protectors,'' which is 
believed to yield data that more closely mirrors the ``real world'' 
effectiveness of hearing protector devices.
    The principal concern with S3.19-1974 is its requirement that 
testing laboratory personnel (hereinafter the experimenter) physically 
fit the HPD on the human test subject. The basis for using human test 
subjects is to address the range of differences in both the external 
and internal structure of the human ear. Clearly, the original intent 
of the experimenter fitting the device was to minimize the variability 
of product effectiveness that could occur due to the user's lack of 
skill in fitting the device and not that due to the sound reduction 
effectiveness of the device itself when used as instructed by the 
manufacturer. However, this procedure can lend itself to experimenter 
fit adjustments of the product on the test subject to achieve the 
maximum sound reduction possible without regard for a test subject's 
comfort or intended fit. Finally, a major deficiency of ANSI S3.19 with 
regard to current and potential future products is its inability to be 
used to determine the performance of special devices, such as those 
utilizing active noise reduction and those used in high level impulsive 
noise fields.
    EPA agrees with interested parties that the current required test 
methodology, based upon ANSI S3.19-1974, can result in unrealistically 
high sound reductions that are generally not attainable in real world 
use. The resultant labeled NRR can lead to product selections that may 
leave users under-protected and subject to potential hearing damage. 
Further, the procedure lacks suitability for the testing of other than 
passive devices. For these reasons, the EPA has concluded, subject to 
consideration of public comment, that ANSI S 3.19-1974 is no longer 
appropriate for HPD label requirements.

D. Test Subjects

    ANSI S3.19-1974, requires 10 subjects to be tested regardless of 
the type of protector. Each subject is tested three times and their 
mean attenuations and standard deviations are determined without 
averaging the individual subject results. Interested parties have 
suggested that more test subjects should be utilized for passive insert 
devices in order to achieve a more statistically accurate 
representation of the user population. They also proposed that each 
test subject be required to undergo multiple tests on each product in 
order to obtain an average fit sound reduction value. They have also 
suggested that fewer test subjects be required for devices that fit 
over the user's ears (ear muffs) because such protectors require 
minimal user skill in obtaining a proper fit.
    The EPA favors any changes in the testing protocol that will 
improve the quality of information that can be provided to the ultimate 
user of an HPD while offering the potential for reduced testing costs.

E. Compliance Testing

    The current regulation was written at a time when, in large part, 
ear plugs made of wax-impregnated cotton,

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silicon, early formulas of polyurethane foam, and earmuffs, were the 
only types of products on the market. For many reasons, too numerous to 
detail here, the EPA decided to require compliance testing of a HPD 
only once prior to its entry into commerce. Further tests are required 
if (1) a manufacturer modifies the design or changes materials or 
structure such that the acoustic performance of the product may be 
degraded; (2) the Administrator has reason to believe the original 
effectiveness rating is in error, or otherwise requires information 
pursuant to section 13 of Noise Control Act; or (3) a selective 
enforcement audit revealed products in non-compliance with their 
labeled information. With the entry of many new HPD materials, designs, 
and electronic and mechanical systems, the Agency has become concerned 
with the adequacy of its present once in a product lifetime test 
requirement.

 IV. Product Applicability

    This proposed regulation would apply to all devices or materials 
sold as explicit or implicit ``hearing protection devices'' on the 
basis of their ability to reduce the level of sound entering the user's 
ears and thus serve to protect the user's hearing. The proposed 
regulation also applies to devices whose primary function may not be 
hearing protection, but which are nonetheless sold in-part as providing 
protection to the user's hearing.
    To the extent that a product manufacturer, importer, packager or 
any other party introduces into U.S. commerce any product that 
incorporates an explicit or implicit claim that the product can protect 
the hearing of the user or stipulates the level of sound reduction 
offered by such product, then it would be subject to the requirements 
of this proposed regulation.
    The Agency has attempted to establish product definitions on the 
broadest basis in order to capture all current and future HPD designs 
and characteristics. The EPA recognizes that by taking this broad 
approach, certain products presently on the market, that are intended 
to provide a level of comfort for sleeping, listening to music, 
restricting the entry of water into ears during swimming or bathing, 
etc., may be captured as possible hearing protectors. As stated above, 
this rule does not apply to those devices or materials.
    While not necessarily a complete listing, the general categories of 
hearing protector devices that are subject to this proposed regulation 
are described below:
    (1) Passive Hearing Protection Device. A device that relies solely 
on its structural elements to block or otherwise control the 
transmission of sound into the ear canal and that does not use 
electronic circuits or acoustic elements to reduce the entry of 
external sound.
    (2) Active Hearing Protection Device. A device that contains 
electronic components including transducers (i.e. speakers and 
microphones) to increase or decrease the transmission of sound into the 
ear canal. Also referred to as an electronic hearing protection device.
    (3) Ear plug. A hearing protection device that is designed to be 
inserted into the ear canal and held in place principally by virtue of 
its fit inside the ear canal.
    (4) Ear muff. A hearing protection device usually comprised of a 
headband which applies spring-like force/pressure to two ear cups with 
soft cushions to seal against the external ear or pinna (supra-aural) 
or the sides of the head around the pinna (circumaural). The ear cups 
may also be held in position by attachment arms mounted on a hardhat or 
hardcap.
    (5) Active Noise Reduction Hearing Protection Device. A device that 
uses single or in combination, electrical and structural elements to 
reduce the sound transmitted to the ear canal through acoustic 
cancellation of the air-conducted and/or bone-conducted external sound.
    (6) Amplitude Sensitive Hearing Protection Device. A device that is 
designed to produce a change in sound attenuation as a function of the 
external sound level.
    (7) Communication Headset. A voice communication device (ear plug, 
ear muff, semi-insert device or helmet) that is designed also to reduce 
the level of sound at the users' ears by either structural elements 
and/or electronic means.
    (8) Custom-molded Hearing Protection Device. A device that is made 
to conform to a specific person's ears (pinnas) and ear canals.
    (9) Helmet. A hearing protection device that provides impact 
protection to the head or skull and that is designed also to reduce the 
external sound through either structural elements and/or electronic 
means.
    (10) Semi-insert Device. An ear plug-like hearing protection device 
consisting of soft pods or tips that are held in place by a lightweight 
band. The pods are positioned in the conchae covering the entrances to 
the ear canals, or fitted to varying depths within the ear canals. 
Semi-inserts that cap the canal require the force of the band to retain 
their position and acoustic seal. Semi-inserts that enter the canal 
behave more like ear plugs; they seal the ear to block noise with or 
without the application of band force. Also referred to as canal cap or 
banded hearing protector.

V. Incorporation by Reference

    The test methodologies that are being proposed in subpart B rely in 
whole or in part on established consensus standards of the American 
National Standards Institute (ANSI) and design standard of the 
International Electrotechnical Commission (IEC). The version of the 
standards that are incorporated in the rule remains the applicable 
standard unless and until the EPA amends the rule to reflect any change 
in the test procedures. In recognition of the copyrights that protect 
these standards, the Agency is ``incorporating by reference,'' into 
subpart B, the following ANSI and IEC standards:
    (1) ANSI/ASA S12.6--2008, ``Methods for Measuring the Real-Ear 
Attenuation of Hearing Protectors''
    (2) ANSI S12.42--1995 (R2002), ``Microphone-in-Real-Ear and 
Acoustic Test Fixture Methods for the Measurement of Insertion Loss of 
Circumaural Hearing Protection Devices''
    (3) ANSI/ASA S12.68--2007, ``Methods of Estimating Effective A-
weighted Sound Pressure Levels When Hearing Protectors are Worn''
    (4) IEC 60711, ``Occluded-ear simulator for the measurement of 
earphones coupled to the ear by ear inserts''

VI. Test Methodologies

    The EPA has determined, after extensive investigations, multi-
laboratory testing and discussions with experts in the field, that the 
following test methodologies are appropriate for use on the broad 
spectrum of present and potentially future materials and devices that 
are sold wholly or in-part on the basis of their ability to reduce the 
level of sound entering the human ear.
    Further, to avoid the potential creation of a technical barrier to 
U.S. manufacturers' global trade, the Agency has considered foreign 
testing and labeling standards regarding HPD rating schemes and their 
relationship to the U.S. Noise Reduction Rating (NRR). In that regard, 
the Agency has given particular attention to the International 
Standards Organization (ISO) standard 4869, parts 1 and 2 which 
describe, for the most part, the European testing and rating methods 
for HPDs. ISO 4869 part 1 permits subjects to be experienced and 
trained in proper product use technique.

[[Page 39154]]

However, the Agency has concluded that the referenced ISO standards do 
not add substantively to the intended testing and rating objectives of 
the proposed regulation over that offered by the selected ANSI 
standards.
    The Agency's consideration of ANSI S12.6-2008 was preceded by 
considerable debate within the hearing protector device community 
regarding the qualifications of the human test subjects. ANSI S12.6-
2008 offers two significantly different testing protocols, Method A and 
Method B, as they relate to prior experience of the test subjects and 
role of the experimenter in the preparation of test subjects prior to 
product testing. In brief, Method A test subjects are informed and 
experienced regarding the use of HPDs, based upon detailed instruction 
and demonstration from the experimenter or from previous HPD use. 
Method B test subjects are selected principally because of their lack 
of prior knowledge and experience with HPDs. They are not provided any 
guidance from the experimenter with regard to product use, beyond that 
given by the manufacturer's normally provided written instructions. 
There was no consensus on whether EPA should require Method A or Method 
B.

A. Method Selection

    Several factors must be considered in the selection of testing 
protocols. First, the measured sound attenuation is the principal 
determinant of the potential noise reduction rating (effectiveness) of 
the device. Second, the variability of the rating metric, which is 
primarily a function of subject selection and training and test 
laboratory practices, must be accounted for. Third, to the extent 
possible, the test method should give a measure of product 
effectiveness under real-world use conditions. Finally, the method 
should provide a reliable and repeatable means for assessing product 
performance, with minimal influence and impact of non-product related 
factors. The competing methods and their differing means to account for 
user capabilities are presented below.
1. Method A
    Supporters of Method A believe it is the appropriate protocol to 
assess the acoustic performance and sound attenuation capability of an 
HPD attributes that are a function of product design, materials and 
construction, rather than user skills. When subjects are trained in the 
proper use of hearing protectors, they demonstrate higher average 
attenuation for devices such as earplugs and semi-aural inserts than do 
``inexperienced'' subjects. In the EPA-sponsored interlaboratory 
studies, earmuffs exhibited little change in attenuation between 
experienced and inexperienced test subjects. However, for earplugs and 
semi-aural devices, there were marked improvements in attenuation when 
Method B subjects were given training; attenuation results for foam 
roll-down earplugs showed significant improvement as a result of 
correct fit. The range of attenuation results tended to be larger with 
Method A, but the variability across test subjects was reduced markedly 
from that of Method B.
    Method A is similar to the International Standards Organization 
(ISO) test standard 4869-1 that permits subjects to be experienced with 
the use and fitting of protectors. The Occupational Safety and Health 
Administration (OSHA) and the military require training in the use of 
hearing protectors, thus supporting the use of Method A that reflects 
the attenuation obtained by trained users. Supporters also maintain 
that Method B is an assessment of the product's ergonomics and 
manufacturers' instructions, but not necessarily the products' noise 
reduction capabilities. Thus, the use of inexperienced subjects 
increases the variance of the attenuation data and may serve to mask 
procedural variances between testing laboratories. Finally, they 
expressed concern that selection of a Method-B rated protector could 
result in user over-protection due to the understated attenuation 
results from inexperienced subjects. This, in turn, can lead to 
potential safety hazards, particularly in those noise environments that 
rely on speech communications and audible warning signals.
2. Method B
    Supporters of Method B maintained that the use of inexperienced 
test subjects is a better predictor of the level of sound reduction 
(attenuation) that might be expected by users in the real world as 
opposed to the laboratory. Data from field studies show slightly lower 
real-world attenuation than the laboratory data using Method B, and 
even studies of well-trained users (as opposed to test subjects) showed 
results similar to Method B data. Further, it appears that the rank 
ordering of hearing protector attenuation using Method B correlates 
well with the data from field studies. While Method-B results exhibited 
better reproducibility, the measured attenuations were lower. Finally, 
the variability of the Method-B results was greater than that of 
Method-A results.
    Method B supporters also suggest that the use of subject fit 
testing methods will eventually lead to protector designs that 
facilitate the user fitting the protector correctly.
3. Training
    Although disagreement exists between Method A and B supporters and 
parties that will be affected by this revised regulation, there is 
common agreement that the ultimate effectiveness of a product can only 
be realized with proper training or, at a minimum, user-friendly 
instructions. The Department of Defense (DOD) requires that enlisted 
personnel, officers, and civilians who are exposed to noise receive 
instruction in the proper use and maintenance of hearing protectors. 
The OSHA requires that workers involved in a hearing conservation 
program be instructed about the harmful effects of noise and trained in 
the proper use of hearing protectors. NIOSH recommends that training is 
an essential element of every hearing loss prevention program, along 
with noise control engineering and administrative measures to prevent 
hearing loss. Finally, the National Hearing Conservation Association 
(NHCA) recommends that training in the proper use of hearing protectors 
be provided to noise-exposed persons.
4. Test Protocol Selection
    The EPA is proposing to adopt the ANSI S12.6-2008--Method-A testing 
protocol for all hearing protectors in their ``passive'' mode. EPA 
believes, subject to consideration of public comment, that Method A is 
more appropriate to the intent and fulfillment of the hearing protector 
labeling program objective--to provide an accurate assessment of the 
acoustic performance of only the product (see section 8(b) of the Act, 
authorizing labeling which describes a product's ``effectiveness in 
reducing noise'').
    EPA agrees that Method B can more nearly represent the anticipated 
protection for uninformed HPD users. But it is not reasonable to assume 
that HPD users will be typically uninformed, or that they would remain 
so as they grow accustomed to the use of an HPD. In fact, the federal 
labeling regulation is but one leg of a three legged stool and is not 
intended to be all-encompassing in the prevention of hearing damage or 
loss. The other two legs of a hearing conservation program must include 
user training and, to the extent possible, engineering controls of 
noise.
    The Agency has several concerns with the use of Method B. First, it 
believes the concept of ``na[iuml]ve'' test subjects, as prescribed in 
ANSI S12.6, is not appropriate for the determination of a

[[Page 39155]]

product's acoustical performance, absent human intervention. EPA 
believes that the naivety of the test subject (hereinafter 
``inexperienced'' test subject) disappears (or is at least reduced) 
once the test subject has completed his or her first series of tests. 
Consequently, the use of such subjects for multiple testing of similar 
products is questionable regarding their inexperience. Second, based 
upon results from an EPA sponsored and NIOSH managed multi-laboratory 
test \4\ of six different products, significant differences in 
technique between testing laboratories became evident from Method A 
data. However, such differences appeared to be masked by the large 
variability between test subjects based upon Method B data. Third, the 
Agency believes the true potential effectiveness (NRR) of the HPD, when 
used correctly as instructed by the manufacturer, could be understated 
because of low attenuation measurements that resulted from improper fit 
by inexperienced test subjects; this is particularly important with ear 
insert HPDs.
---------------------------------------------------------------------------

    \4\ National Institute for Occupational Safety and Health 
(NIOSH)/EPA Interlab Study Comparison of ANSI S12.6, Method A and B. 
Refer to the Federal Docket at https://www.regulations.gov, docket 
number EPA-HQ-OAR-2003-0024.
---------------------------------------------------------------------------

    Further, EPA agrees with supporters of Method A regarding potential 
over-protection as a result of user selection based on a low Noise 
Reduction Rating determined from Method B testing. EPA believes the HPD 
rating should show, within a reasonable range, the sound reduction that 
users can expect to receive when the device is worn as instructed by 
the manufacturer. Since EPA cannot regulate human behavior nor provide 
training in the proper use of HPDs, its only regulatory option is to 
provide the most accurate product performance information available and 
rely on training from other entities to assure proper use. It is on the 
above basis that EPA is proposing to require the use of Method A.
    Finally, in the absence of suitable ANSI or other recognized 
testing standards that address devices that incorporate electronics to 
enhance their sound reduction (attenuation) performance (i.e., 
``active'' mode) or that are intended for use in extremely high 
impulsive noise environments (levels greater than 140 decibels), the 
Agency, in collaboration with NIOSH and the U.S. Air Force, has 
developed test methods for these devices. An explanation of these 
``non-consensus standard'' test protocols is given below. The EPA is 
seeking comment on these new test protocols.

B. Proposed Testing Protocols

1. Passive Noise Reduction Testing
    As stated above, EPA is proposing that ANSI 12.6-2008, Method A, 
Real Ear Attenuation at Threshold (REAT) test protocol be used for the 
determination of the passive noise reduction performance of all 
categories of hearing protector materials and devices. The key elements 
of the REAT test method includes:
 Subject Selection and Qualification
 Fitting Protocol
 Test Procedure
 Reporting of Test Data
a. Subject Selection and Qualification
    The ANSI S12.6-2008 standard specifies test subject requirements 
for the Method-A protocol. Subjects must have pure-tone air conducted 
hearing thresholds better than 25 dB HL (Hearing Level) in both ears. 
Subjects must also demonstrate their proficiency in obtaining a hearing 
threshold in the test environment with the specific equipment used in 
the testing laboratory. Proficiency is demonstrated through repeated 
threshold testing without hearing protectors being worn such that the 
subject has a range of thresholds that does not exceed a difference of 
5 decibels for each test frequency. The Agency believes that subject 
selection criteria can be used to identify a population of test 
subjects that produce high attenuations and which have a narrow range 
of attenuations across subjects. Therefore, the Agency will permit 
subjects to be rejected for various physical reasons during the pretest 
process, but they may not be removed from the pool of tested subjects 
due to their poor attenuation results.
b. Fitting Protocol
    Under the 1979 regulation, the fitting protocol requires an 
experimenter-fit method. The subject serves as an acoustical test 
fixture capable of providing a response to the test stimulus. The 
experimenter places the protectors on the subject's head or in the 
subject's ear canals and prohibits the subject from making any 
adjustments to the fit of the product. This practice provided a 
repeatable measurement of the maximum attenuation that a product could 
achieve for deeply inserted earplugs. For devices such as earmuffs and 
semi-aural inserts, the ability to achieve a greater attenuation was 
less susceptible to experimenter manipulation.
    The proposed ANSI S12.6-2008 Method-A incorporates specific 
instructions for the experimenter and limits the interaction between 
the subject and experimenter once training in the use of the product is 
completed. The process of defining how a subject should be trained was 
found to be more complex than defining the process for an inexperienced 
subject. The Working Group responsible for the development of ANSI 
S12.6-2008 Method-A settled on an approach that in many ways reflects 
the reality of how protectors should be issued to noise-exposed 
persons. The experimenter is allowed to provide training to the subject 
in how to best fit and use the specific hearing protector. However, 
once the subject enters the test room, the experimenter is prohibited 
from providing further instruction. When one considers how protectors 
are distributed and worn in most settings, if any training is given, it 
generally is of a short duration and the user must ultimately fit the 
protector on his/her head or in their ear canals.
c. Test Panel Size
    The protocol stipulated in the 1979 regulation specifies that ten 
subjects are to be tested three times for occluded and unoccluded 
thresholds and, upon their meeting specified hearing criteria, be 
selected as the test panel. These requirements were based upon research 
conducted by the U.S. Air Force and represented the best estimates of 
variability available in 1979. Since that time, the ANSI S12, Working 
Group 11 determined that 20 subjects are statistically appropriate for 
testing ear plugs and semi-aural inserts and 10 subjects are 
appropriate for ear muffs. The most recent interlaboratory study 
conducted by EPA and NIOSH found that 20 subjects were adequate for 
repeatable intra-laboratory tests with both Method-A and Method-B 
protocols.\5\ Section 5.8, ``Number of subjects'', of ANSI S12.6 
requires that 10 subjects be tested for earmuffs or helmets and 20 
subjects for each test on earplugs or semi-insert devices.
---------------------------------------------------------------------------

    \5\ National Institute for Occupational Safety and Health 
(NIOSH)/EPA Interlab Study Comparison of ANSI S12.6, Method A and B. 
Refer to the Federal Docket at https://www.regulations.gov, docket 
number EPA-HQ-OAR-2003-0024.
---------------------------------------------------------------------------

    Questions have been raised about the appropriate number of subjects 
to be used in certain circumstances. It has been suggested that the 
regulation allow manufacturers to increase the sample size 
indefinitely, with the proviso they report to EPA the total number of 
subjects tested for each HPD. The Agency is not opposed to this latter 
approach provided the test data from all subjects is included in the 
calculations leading to the NRR. However, at this time the EPA is 
proposing to adopt the

[[Page 39156]]

requirements for 10 and 20 test subjects as specified in ANSI S12.6, 
Section 5.8. The Agency will consider comments on this topic.
d. Test Room Environment
    EPA is proposing to change the requirements of the test room 
environment from those specified in ANSI S3.19-1974. Changes of 
particular note are the reverberation time of the room and the 
characterization of the sound field with respect to uniformity and 
diffusivity; both parameters are more specific under ANSI S12.6-2008. 
The procedure to determine the occluded and unoccluded thresholds is 
defined as a modified Bekesy procedure. This procedure was not selected 
on the basis of superior psychophysical techniques, but was selected by 
the ANSI S12 Working Group because most of the testing labs used a 
variant of the method; variation across testing labs could be minimized 
by standardizing the method.
e. Test Frequencies
    The ANSI S3.19-1974 standard required the REAT test include 
attenuation measurements at 3150 and 6300 Hz. However, later analysis 
\6\ of the added benefit realized by the current NRR due to the 
inclusion of test frequencies at 3150 and 6300 Hz, revealed differences 
on the order of 0.1 to 0.3 decibels. NIOSH conducted a similar analysis 
on 435 devices listed in the NIOSH Compendium \7\ of Hearing Protection 
Devices and confirmed the earlier results. Thus, the voluntary 
standards community concluded that the small differences in the NRR 
through the inclusion of these two added test frequencies do not 
justify the additional time and effort in testing subjects at those 
frequencies. Consequently, in the recent versions of ANSI S12.6 the 
requirement to test at 3150 and 6300 Hz has been eliminated for REAT 
measurements. The Agency concurs with these findings and is proposing 
to no longer require tests of attenuation at 3150 and 6300 Hz.
---------------------------------------------------------------------------

    \6\ Murphy WJ, ``Analysis of the necessity to test at 3150 and 
6300 Hz and the effect on the Noise Reduction Rating.''
    \7\ Franks JR, Graydon PS, Jeng C, Murphy WJ, ``NIOSH Hearing 
Protector Device Compendium,'' https://www2d.cdc.gov/hp-devices/hp_srchpg01.asp (2003). as of July 6, 2008.
---------------------------------------------------------------------------

f. Computation of the Noise Reduction Rating (NRR)
    The 1979 regulation requires the NRR be computed with the mean 
attenuations and standard deviations from all test subjects at each 
frequency band. The ANSI S12.68-2007 standard requires that data from 
the individual subjects be used in determining a device's rating across 
a range of different noise spectra. The inclusion of both subject and 
spectral variability provides results that are more representative of 
the product's performance when used by different persons in different 
types of noise environments.
    The Agency is proposing that the ANSI S12.68 methods be used to 
compute the required NRRs for Passive hearing protectors on the basis 
that such NRRs provide the best available means of describing product 
performance that is likely to occur in real-world environments.
2. Active Noise Reduction Testing
    Active Noise Reduction (ANR) devices require additional 
measurements beyond those described above for the passive attenuation 
methods. An ANR device utilizes electronic circuitry to sample an 
external sound signal, analyzes the principle acoustic component(s), 
and then generates a 180 degree out-of-phase signal to be played into 
the occluded volume (the space under the protector) that, in effect, 
cancels the external signal that is present under the protector. An 
error correction microphone in the occluded volume is used to determine 
the effectiveness of the control, thus allowing adjustment of control 
parameters to maximize effectiveness.
    ANR circuitry has been incorporated in both earplug and earmuff 
HPDs in several forms; digital or analog controls or a combination of 
the two have been used. Digital control circuits tend to isolate 
specific tonal components of the external sound and effect a 
significant noise reduction. Analog circuits tend to be simpler to 
implement and have a broader share of the market. The type of control 
can be feedback, feed forward or a hybrid of the two. In a feedback 
circuit, the signal must be sampled in the occluded volume and the 
control is based upon the error correction microphone. In a feed 
forward circuit, the external microphone is sampled and the control is 
predicted. The error correction microphone is used to help the circuit 
determine the effectiveness of the control.
a. Test Method Design Parameters
    ANR devices pose a particular problem when attempting to determine 
a noise reduction rating. The use of a REAT procedure yields an 
attenuation setting for the device that is biased due to the residual 
noise produced by the ANR circuitry. When activated, ANR devices tend 
to produce a small level of electronic noise that is audible in quiet 
environments. Because REAT testing requires the test subject to 
identify the presence of a sound produced by electro-mechanical 
speakers in the test environment, any sound produced by the hearing 
protector can interfere with the ability to measure near the subject's 
threshold of hearing, resulting in an inaccurate assessment of the 
device's active noise reduction performance. An alternative method for 
determining the noise reduction of the active device is to utilize the 
Microphone In Real Ear (MIRE) technique where a small microphone is 
placed in the subject's occluded volume and the insertion loss (the 
difference in noise level when the device is activated and not 
activated) is measured. Alternatively, the transmission loss (the 
difference in noise levels between the external sound field and 
occluded volume) can be measured. A potential limitation of the MIRE 
technique is that it underestimates noise reduction at low frequencies 
when compared to the REAT method.
    The use of the MIRE technique for earmuff ANR devices can be 
readily applied since the occluded volume is sufficiently large that a 
miniature microphone can be placed completely within the earmuff and 
positioned in the ear canal without interfering with the seal of the 
muff cushions to the side of the head. The diameter of the lead wires 
to the MIRE microphone can be small enough such that no gaps in the 
seal will be created. Alternatively, the MIRE microphone can be 
wireless, thus eliminating the need for any wires to exit underneath 
the cushions of the ear muffs.
    In the case of ANR earplugs, the use of a MIRE measurement becomes 
complicated. Some prototypes rely on a deep-insertion custom-molded 
earplug that houses the electronic package. For these devices, the 
occluded volume may only be 0.5 cubic centimeters. Placement of the 
miniature microphone in the occluded volume could adversely affect the 
operation of control circuits designed for a specific occluded volume. 
If the test method uses a probe microphone, then the probe either has 
to be placed alongside the earplug or must be passed through a sound 
bore in the device. Placement of a probe microphone alongside the 
earplug creates a potential leakage path that changes the acoustic 
impedance of the occluded volume. Requiring a sound bore through the 
device deprives the manufacturer of critical volume within the device 
that may be necessary to house additional circuitry. The seal of

[[Page 39157]]

the sound bore with the probe tube can also present a sound leakage 
path.
    The Agency has received input from researchers in the field of 
active noise reduction hearing protection devices and has determined 
that the method to evaluate ANR noise reduction must include a 
combination of both the REAT and the MIRE techniques. As stated 
earlier, every hearing protector manufacturer would be required to 
conduct a REAT passive measurement and publish a passive NRR. 
Consequently, a REAT tests would have to be carried out on all ANR 
devices with their electronic circuitry turned off.
    For ANR earplugs, the active contribution would be measured on an 
acoustic test fixture. The test fixture would include artificial ear 
canals (tapered cylinder) and ear simulators that approximate the 
occluded volume and acoustic impedance of the human ear; such devices 
are commercially available.
    For earmuffs, the method uses the same test subjects who 
participated in the REAT testing. MIRE microphones are mounted on ear 
plugs underneath both the left and right ear muffs and the microphones 
are centered in the ear canal flush with the floor of the concha.
    To overcome the discrepancy between MIRE and REAT, the MIRE 
technique would be used to measure the active contribution to the total 
HPD noise reduction. In both the earmuff and earplug cases, the device 
would be assessed with the electronics turned on and off in a broadband 
noise field. The difference between the noise levels measured in the on 
and off conditions are calculated to estimate the active attenuation 
contribution. The active contribution is added to the attenuations 
measured with the REAT method. Together, these attenuations for each 
subject would be used to estimate the NRR according to the ANSI S12.68-
2007 method.
b. Method Requirement
    No standardized testing method(s) has yet been developed for 
determining the peak noise reduction of hearing protection devices. 
Several organizations have investigated a range of impulse generation 
techniques. University of Florinapolis, Brazil has a large diameter 
acoustic shock tube in which a mannequin head can be placed to test the 
performance of a protector.\8\ The Finish Institute of Occupational 
Health and the Polish Central Institute for Labour Protection have 
reported the attenuation of hearing protectors exposed to an acoustic 
shock tube.9 10 The French German Research Institute de 
Saint Louis (ISL) evaluates hearing protector performance with 
explosives and an anthropometric mannequin with an embedded ear 
simulator. The US Army has conducted mannequin measurements with 
explosives and also with an acoustic shock tube. The US Air Force has 
also evaluated protectors on a mannequin with an explosive impulse 
source. NIOSH has conducted exposure measurements for gunshots and 
various occupational impulsive noises and has utilized a 
mannequin.11 12 The use of a mannequin with simulated ears, 
in place of human test subjects, is essential to avoid the risk of 
hearing damage at the required high impulse sound levels.
---------------------------------------------------------------------------

    \8\ Birch RS, Gerges SN, Vergara EF, ``Design of a pulse 
generator and shock tube for measuring hearing protector attenuation 
of high-amplitude impulsive noise'' Appl. Acoustics 64:269-286 
(2003).
    \9\ Parmentier G., Dancer A., Buck K., Kronenberger G., Beck C., 
``Artificial Head (ATF) for Evaluation of Hearing Protectors'' 
Acustica,Volume 86 (2000).
    \10\ Zera J. and Mlynski R. ``Attenuation of high-level impulses 
by earmuffs'' J. Acoust. Soc. Am. 122:2082-2096 (2007).
    \11\ Tubbs RL, Murphy WJ, ``Health Hazard Evaluation Report 
2002-0131-2898 Fort Collins Police Services, Fort Collins Colorado'' 
DHHS-CDC-NIOSH, HETA 2002-0131-2898 (2003).
    \12\ Harney J., King B., Tubbs R., Crouch K., Hayden C., Kardous 
C., Khan A., Mickelsen L., Willson R., ``Health Hazard Evaluation 
Report 2000-0191-2960 Immigration and Naturalization Service, 
National Firearms Unit, Altoona, PA'', DHHS-CDC-NIOSH, HETA 
2000-0191-2960 (2005).
---------------------------------------------------------------------------

    Berger \13\ published a review of methods for measuring attenuation 
of hearing protection devices and has noted that one problem common to 
many of the artificial ear or head test fixtures available at that time 
was a lack of isolation of the sensing microphone. The purpose of the 
mannequin or test fixture is to determine the performance of the air 
conducted pathway of the device. Berger previously identified that bone 
conduction of the impulse through the skull was a limiting factor for 
hearing protector performance. Thus, the test fixture must incorporate 
isolation of the acoustic sensors from mechanical vibrations that are 
analogous to that of bone conduction.
---------------------------------------------------------------------------

    \13\ Berger, E. ``Methods of measuring the attenuation of 
hearing protection devices'', J. Acosut. Soc. Am. 79:1655-1687 
(1986).
---------------------------------------------------------------------------

    Currently there are several mannequins (test fixtures) available 
for acoustic research as well as other fixtures of varied design that 
could be potentially used to determine peak sound reduction. Three of 
the most well-known mannequins are the G.R.A.S. KEMAR (Knowles 
Electronic Manikin for Acoustic Research), the Bruel and Kjaer HATS 
(Head and Torso Simulator) and the Head Acoustics RMS fixture. 
Parmentier et al. reported that the isolation of the KEMAR and the 
early model of the Head Acoustics fixtures did not achieve sufficient 
isolation to get below bone conduction.\14\ The HATS device suffers 
from a similar problem as KEMAR; the volume of the head is devoid of 
any sound or vibration absorbing mass. Parmentier et al. isolated the 
ear simulator inside a suspended capsule within a relatively solid 
acrylic body. The additional features were the use of a replaceable ear 
canal and pinna set which allow both muffs and plugs to be tested. The 
ISL mannequin has the added benefit of being anthropometrically correct 
and thus more nearly simulates sound diffraction effects around the 
head.
---------------------------------------------------------------------------

    \14\ Parmentier, G., Dancer, A., Buck, K., Kronenberger, G., and 
Beck, C. (2000). ``Artificial Head (ATF) for Evaluation of Hearing 
Protectors,'' Acta Acustica 86(5), 847-852.
---------------------------------------------------------------------------

a. Test Procedure
    The proposed test procedure consists of three parts: calibration, 
data collection from a hearing protector exposed to the impulse sound 
source and computation of the of the peak noise reduction.
    Calibration is accomplished by simultaneously measuring sound 
impulses having a peak sound pressure level (SPL) of approximately 150 
dBA. The pulse waveforms at both the free-field source location and the 
impulse acoustic test fixture (IATF), without a protector in place 
(unoccluded), are recorded. For consistency, five impulses are 
electronically captured and their waveforms analyzed to obtain the real 
and imaginary components necessary to calculate an acoustic transfer 
function. This transfer function will be used to transform the free-
field impulse waveforms to their equivalent impulses at the IATF during 
the conduct of occluded tests. This impulse calibration and 
transformation is essential to the determination of a hearing 
protector's effectiveness in high sound level impulse environments.
    The second part of the proposed test procedure is the determination 
of the peak sound reduction provided by a hearing protector for 
different peak impulse levels. For this part of the procedure, three 
ranges of impulsive sound levels are required: 130 to 134, 148 to 152 
and 166 to 170 dBA peak sound pressure level. The specified ranges of 
impulse sound levels approximate the peak impulse levels created by a 
wide variety of everyday sources e.g. pneumatic tools, powder-

[[Page 39158]]

actuated tools, construction equipment, firearms and fireworks.
    The hearing protector is installed on the IATF, the particular SPL 
range is selected and the impulse sound source is activated. The free 
field and IATF impulse waveforms are electronically captured 
simultaneously with their respective microphones. The Agency has 
determined that for each sample type a minimum of five protectors will 
be tested. Each protector will be removed and refitted on the IATF for 
testing at each of the three impulse SPL ranges.
    The third part of the proposed procedure is the calculation of the 
impulse sound reduction. The transfer function computed from the 
calibration waveforms is used to transform the free-field impulses to 
their counterparts at the location of the IATF microphone, absent the 
acoustic disturbances that result from the IATF. The transfer function 
effectively yields a filter that adjusts both the frequency amplitude 
response and the phase response of the free-field wave to account for 
differences due to the response of the ear simulator and resonance of 
the IATF ear canal. The waveforms from the IATF measured underneath the 
hearing protector and the transformed free-field waveforms are 
evaluated to identify the maximum peak sound pressures in both pairs of 
waveforms. The difference in decibels yields the peak reduction for a 
single trial of a protector and impulse SPL range. Once each of the 
waveform pairs has been evaluated, the maximum and minimum peak sound 
reductions across the range of levels would be determined for use in 
developing the NRRs.
d. Computation of the Noise Reduction Rating (NRR)
    Manufacturers of amplitude sensitive devices are required to 
measure the passive REAT performance levels under the device with the 
electronics turned on and turned off for all test subjects. For ear 
muffs and helmets, where it is possible to use the MIRE technique, the 
levels will be measured for all test subjects. For ear plugs, the 
testing lab is required to perform repeated placement and replacement 
fittings of the device on the acoustic test fixture. The laboratory 
must conduct as many repeated measurements as required for the number 
of subjects tested.

VII. Noise Reduction Rating Strategies

    This proposed regulation sets forth a new rating scheme that, while 
preserving the current NRR rating metric (e.g. a numeric rating of 
effectiveness), is expanded to provide the ultimate user and hearing 
conservation specialist with additional information regarding the 
potential range of protector effectiveness based on the users' ability 
to achieve proper fit.
    The single number Noise Reduction Rating has been the focus of 
attention since promulgation of 40 CFR Part 211 subpart B, in 1979. 
Initial concerns ranged from a lack of understanding of the 
relationship between NRR and hearing protection, to concerns that such 
numeric ratings would result in a ``rating war'' within the hearing 
protector industry. While both situation