EPA 550/9-77-252

             FOR THE
             APRIL 1977
     U.S. Environmental Protection Agency
     Office of Noise Abatement and Control
         Washington, D.C. 20460

                                            EPA 550/9-77-252

                   FOR THE
                  APRIL 1977
                  Prepared By
       Office of Noise Abatement and Control
   This document has been approved for general availability.
   It does not constitute a standard, specification or regulation.

     This Background Document has been prepared by the Environmental
Protection Agency in support of the Proposed Noise Labeling Standards
for Hearing Protectors. The proposed regulation will be promulgated
under the authority of sections 8, 10, 11 and 13 of the Noise Control
Act of 1972.



I.    Statutory Basis	1

II.   Rationale for Labeling Hearing Protectors 	  3

III.  Methodology of Regulatory Development 	  4

IV.   Description of Hearing Protective Devices
      and Their Performance Characteristics 	  6
            Introduction  	 ....  6

            Description of Available Devices 	     7
                 Ear Insert Devices  	     8
                 Ear Cap Devices   	.10
                 Ear Muff Devices	    10
                 Combination Devices 	    11

            Factors Affecting Selection of Hearing
            Protective Devices 	    11
                 Attenuation Capability 	    12
                 Use Requirements/Environment  	    13
                 Fitability	    13
                 Comfort	    14
                 Care Requirements	    15
                 Cost	    16
                 Biological Compatibility	    16
                 Durability	    17
                 Summary of Advantages and Disadvantages    18
            Attenuation/Effectiveness of Devices ....    20
                 Factors Affecting Attenuation 	    20
                 Standardization of Attenuation
                 Measurements 	    27
                 Current State-of-the-Art of Hearing
                 Protector Attenuation 	    30
                 Effect of Hearing Protectors on Verbal
                 Communication 	    31

V.    The Hearing Protector Industry 	    38

VI.   Economic Analysis:
            Cost impacts of Hearing Protector Regulation    41

VII.  Bibliography	    46

                            SECTION  I


     With passage of the  Noise Control Act  of 1972  (86  Stat.

1234),  Congress  established a national policy "to promote an
environment for  all Americans free  from noise that  jeopardizes

their  health and welfare."  Section 2 (b) states that ". .  .it

is the purpose of this Act. . .to provide information to the
public respecting the noise emission and noise reduction
characteristics  of. . .products"  (distributed in commerce).

     The requirements and authority to fulfill this  purpose
are delineated in section 8 of the  Act.  This section is

included below,  in its entirety,  as it appears in the Act:


               Sec. 8.  (a)  The Administrator shall  by regu-
           lation 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.
               (b)  For each project  (or class thereof)
           designated under subsection  (a) the Administrator
           shall by regulation require  that notice  be given
           to the prospective  user of the level of  the noise
           the product emits,  or if its effectiveness in re-
           ducing 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.  Sec-
           tions 6(c) (2) shall apply to  the prescribing of
           any regulation under this section.

      In section 10(a) (3) of the Act, entitled, "Prohibited
Acts," Congress declared that it was prohibited for a manu-
facturer to distribute in commerce any new product manufac-
tured after the effective date of a regulation under section
8(b) which is applicable to such product, except in conform-
ity with such regulation."  Section 10(a) (4) further prohib-
its "the removal by any person of any notice affixed to a
product or container pursuant to regulations prescribed under
section 8 (b), prior to sale of the product to the ultimate
      In order to provide incentive for prompt compliance
with the regulations, Congress imposed stiff penalties for
willful violators.  Section 11(a) states, "Any person who
willfully or knowingly violates paragraph (1),  (3), (5), or
(6) of subsection (a) of section 10 of this Act shall be
punished by a fine of not more than $25,000 per day of viola-
tion, or by imprisonment for not more than one year, or by
      It is evident that Congress viewed "labeling" as an
important means of dealing with the problem of noise pollution.

                         SECTION II


      Most people will agree that the ideal method of noise
control is to reduce the level of noise that a source emits.
However, this is often neither technically, nor economically
feasible.  In section 6 of the Noise Control Act, Congress
provided for the regulation of the maximum levels of noise
emitted by newly manufactured products.  These regulations
are to consider best available technology and the cost of
compliance.  It will take a number of years for EPA to develop
these maximum noise emission regulations for all major sources
of noise.  Also, in many cases, technically and economically
feasible noise control measures will not permit sound levels
which totally eliminate detrimental effects upon health and
welfare.  Finally, except for interstate rail and motor car-
riers, these noise regulations will apply only to new prod-
ucts, allowing noisy in-use products to diminish by attrition.
      The most expedient means of reducing our exposure to
harmful and annoying noise which cannot be adequately con-
trolled at the source is through the use of hearing protective
devices.  EPA believes that providing information regarding
the performance of hearing protectors will assist individuals
with this immediate, potentially effective, and relatively
easy and inexpensive method of protection from noise.  There-
fore, EPA has selected hearing protective devices as the first
product for which labeling will be required under section 8
of the Act.

                        SECTION III

      The task of developing product labeling requirements
is divided into two broad areas:  (1) products which emit
noise capable of adversely affecting the public health and
welfare and (2) products which are sold wholly, or in part,
for their effectiveness in reducing noise.  As discussed
above, EPA has selected hearing protective devices which
fall into the second category of eligible products.  The
approach taken in developing these initial labeling require-
ments was to study labeling generally, and concurrently in-
vestigate hearing protectors, specifically.  The purpose was
to permit the developing of a general independent labeling
philosophy, approach, and strategy; and then integrate the
unique aspects of hearing protectors into this framework.
      A consultant was hired to investigate the broad aspects
of labeling as intended under section 8 and to relate these
considerations to issues involved with hearing protectors.
EPA conducted an investigation of the current state-of-the-
art of hearing protectors and available rating schemes for
the purpose of developing a meaningful rating of effective-
ness.  In addition, EPA sponsored an interagency workshop on
labeling to which all Federal agencies involved in labeling
were invited to discuss their experiences.  The purpose of
the workshop was to help the EPA in avoiding any obvious pit-
falls that may previously have been encountered.
      Prior to the effort outlined above, EPA published an
Advance Notice of Proposed Rulemaking in the "Federal Register

explaining, the intent to require labeling of hearing protect-
ors and requesting knowledgeable parties to submit pertinent
information.  Approximately ten responses were submitted
which provided only a limited amount of the information neces-
sary to properly evaluate alternative requirements.   Addi-
tional information was sought by posing a series of questions
to selected companies in the hearing protector industry.
      The more generalized aspects of product noise labeling
mentioned above have been proposed by the Agency in a separate
rulemaking action, entitled Product Noise Labeling - General
Provisions.  That rulemaking action creates a new Part 211 of
the Code of Federal Regulations for all product noise labeling
under section 8 of the Act, and establishes the general pro-
visions of such as Subpart A.  The general provisions have
been utilized in the proposed labeling of hearing protectors
and will be utilized in all further section 8 labeling actions,
For a complete discussion of the General Provisions and their
regulatory development, one should refer to the associated
Notice of Proposed Rulemaking and Background Document for
Product Noise Labeling - General Provisions, 	.

                        SECTION IV

     Recognition of the need for hearing protection dates
back to the early 1900's.  Concern for the need of effective
hearing protective devices appeared first in the armed forces
where cotton wading inserted in the ear was used widely dur-
ing World War I.  In the 1940's, cotton was found to be inef-
fective and consequently, considerable attention was devoted
to developing truly effective devices.  The product of these
early efforts was an earplug known as the V-5IR which is pro-
bably the most widely used earplug today.
     Since 1945, with the rapid growth of technology and
industrialization, noise has been recognized as an occupa-
tional health hazard.  Of greatest concern is the danger of
noise-induced hearing loss.  This has been found to be caused
by permanent damage to the auditory nerve cells which cannot
be corrected at present.  Much research has been conducted to
determine more precisely the effects of noise on humans.
Significant effects in addition to hearing loss have been
observed.  These include headaches, nausea, hypertension,
irritability and diminished work performance.  Growing con-
cern over noise and all workplace environmental hazards cul-
minated with the passage of the Occupational Safety and
Health Act of 1970.  This legislation requires, among other
things, Federal standards for safe noise exposure at the

     With the rapid growth of urbanization and mechanization,
ambient environmental noise rose to levels which created
great public concern.  The hazards of environmental noise to
the public's health or welfare were recognized by Congress
with passage of the Noise Control Act of 1972.
     Thus, the effects of noise exposure have grown from a
military hazard, to an industrial problem, to an insidious
environmental threat to the public's health and welfare.
     The Environmental Protection Agency was designated to
fulfill the mandate of the Noise Control Act.  The Act pro-
vides authority to carry out major responsibilities in two
areas:  (I) regulation of maximum noise emissions from major
sources of environmental noise; and (2) providing information
to the public regarding a product's noise levels or a prod-
uct's effectiveness in reducing noise.  In order to fulfill
the latter function, the Act directs EPA to develop appropri-
ate labeling requirements.  On December 5, 1974, EPA an-
nounced that the first product to be labeled would be hearing
protective devices.

     Over the years, a wide variety of hearing protective
devices have been introduced.  Indeed, virtually anything
that can fit in or over the ear might fall into this category,
In fact, such items as cigarette filters, dimes, pencil
erasers, and cigar butts have been observed in use.  Contem-
porary devices may be classified as 1) ear insert devices,
2) ear cap devices, 3) ear muff devices, and 4) combination

     This type of device is one which is designed to fit into
the ear canal.  A variety of different types of insert de-
vices have been developed.  They may be conveniently dis-
cussed as a) pre-molded, b) malleable, and c) custom molded,

Pre-Molded Inserts
     These devices are uniformly molded of soft, flexible
rubber or plastic compounds.  They are often flanged and corns
in various sizes to accommodate the wide range of ear canal
geometry.  Most pre-molded devices are designed for substan-
tial reuse and, therefore, are washable.  Some of these in-
serts are straight and symmetrical while others are shaped
to conform more to curved ear canals.  A few pre-molded de-
vices are intended for little reuse and can be considered
     Pre-molded insert1devices are relatively inexpensive.
The most varies considerably from devices purchased in bulk
to purchase of a single pair.  In bulk they may cost 10-15C,
while a single pair may cost $1;00.  Often the carrying case
costs more than the device itself.
     These devices when properly cared for are capable of
providing effective hearing protection for extended periods
of time.  The duration is governed primarily by the materials
used which may shrink, crack, or lose their needed resiliency
with time.  Also, due to the small size of these devices,
loss is an important consideration.  Ear wax will cause some
molded plugs to shrink and harden after a period of time.
The wax tends to extract plasticizer from the plug material,,
This will vary from person to person.  Normal life for reus-
able devices can be as los as 5-6 weeks, but for most, it is
about 6 months.

Malleable Inserts
     These devices are, for the most, intended to be dispos-
able.  Their use may range from 1-3 days before replacement
is necessary.  They are made from materials such as plastic
foam, fine glass fibers, and wax-impregnated cotton.  Malle-
able inserts are not sized but rather personally molded to
conform to each individual's ear canal.  This is an advantage
over pre-molded devices, but due to their limited reusability
they are usually more expensive for continuous use.  The cost
per pair ranges from 5-30 cents.  Again, the price depends
upon the quantity purchased.  Since the material must be
kneaded before inserting, proper hygiene is required to pre-
vent the introduction if dirt into the ear canal.

Custom Molded Inserts
     Insert devices which are permanently molded to the exact
shape of an individual's ear are considered custom molded
devices.  Although the process may be somewhat complex, it
basically involves first pressing a pliable material into the
outer ear and ear canal.  This shape is then hardened in some
manner to yield a permanent custom mold.  Typical materialsN
are plastic and silicone compounds.  Hardeners added to these
compounds allow the material to remain pliable long enough
to make the mold and then set permanently after drying.  This
may require a few minutes to a full day.  With proper care
these devices may last from 2-3 years.  Costs may range from
$3.00-$30.00 depending upon the materials, quantities and
source of the labor.  Custom molded devices are generally
more comfortable, but are not necessarily more effective,
than other devices.  They also have the drawback of requiring
greater time and skill in fitting.

     These devices consist of two ear caps fastened to a head-
band which maintains pressure on the caps to seal the outer
edges of the ear canal.  The end of the cap fits slightly
into the ear canal and the balance spreads around the edge of
the canal.  They are molded from soft rubbery material and
fitja large range of ear sizes.  The caps last about 12
months and may be replaced for about $2.00 a pair.  The ini-
tial cost of the device is from $3.00-$5.00.  Ear caps serve
to bridge the gap between inserts and ear muffs, having some
of the advantages and disadvantages of each.  They do not
seem to be in widespread use at the present time.

     These devices fit over the entire outer ear as opposed
to within the ear canal.  They consist of hard molded plas-
tic cups held in place by a spring-loaded headband.  The
cups surround and cover the ear completely, forming a tight
seal around the ear with a flexible vinyl sealing cushion
filled with air, liquid or foam.  Foam fillings are the most
commonly found.  In addition, the cups are lined with an
acoustically absorbent material, usually foam sponge.  The
attachment of the cup to the headband is critical in that it
must allow minimum leakage, while permitting a rather loose
joint to accommodate varying head shapes.  Many devices are
designed to allow the headband to be worn over, under and
behind the head to suit different personal preferences and
use situations.   N                             .
     All parts of the ear muff that contact the skin can be
washed with soap and water.  The rigid ear cups require per-
iodic inspection for cracks or other damage.  The ear seals
are usually the first component to deteriorate generally

from perspiration.  Most ear muffs have replaceable seals
which can extend their useful life indefinitely.
     The price of ear muffs varies in the range of $5.00 to

     There are a number of noisy areas where the need for
hearing protection is compounded by other important require-
ments.  For example, the need for concise communication, the
use of hard hats and the use of welder shields require that
hearing protection be compatible with other personal devices.
Any of the devices mentioned above may be suitable for vari-
ous circumstances.  In certain instances, however, special
modifications and designs are necessary to satisfy the par-
ticular needs.  For example, ear muffs are fitted with com-
munication gear, helmets are designed with built in ear muffs,
hard hats have muffs fastened directly to them and headbands
are shaped differently.  Special care must be taken to ensure
that the needed protection is being provided by these special
purpose devices.

     The most obvious factor to be considered in selecting
the proper hearing protective device is its noise attenuating
capability.  However, there are a number of aspects which, in
certain ways, are equally important as attenuation.  It has
often been quoted that "a good hearing protector is one that
is used," the point being that the user acceptance to wearing
the device is paramount to its effectiveness.  This point of
view arises from the occupational noise situation in which
employers must often seek workers' acceptance of hearing pro-
tection.  Of course, when a person decides to purchase a

hearing protective device, he or she has most likely already
accepted the need and benefits which will be derived from its
use.  Nonetheless, it is important to realize that attenu-
ation is not the only factor to consider.  Further, care must
be taken in selecting hearing protectors because these addi-
tional considerations are either subjective or vary greatly
among individuals.  It is always desirable to provide a choice
of hearing protective devices to suit different individual
preferences, each of which is capable of providing adequate
     The factors which must be considered are:  (1) attenua-
tion capability,  (2) use requirements/environment,' (3) fita-
bility, (4) comfort, (5) care requirements, (6) cost, (7)
biological compatibility, and (8) durability.

     Since attenuation of unwanted noise is the purpose for
which hearing protectors are used, special care must be taken
to ensure that adequate attenuation will be realized by the
user.  The evaluation of attenuation capability has received
considerable emphasis since early development of the devices.
Virtually all tests have been conducted under strictly con-
trolled experimental conditions.  Recently there is concern
that results obtained under these laboratory conditions are
not truly indicative of the attenuation that is realized
under field use conditions.  Attempts are underway to acquire
such field data in order to determine the extent of this
problem.  A field test procedure has been developed under a
grant from the National Institute for Occupational Safety
and Health.
     Due to the importance of the aspect of attenuation, it
will be treated separately in detail in the following section.

     It is necessary to consider the type of use and the con-
ditions under which hearing protectors will be needed.  Such
items as temperature and humidity, intermittent or continuous
use, need for compatibility with other personal safety de-
vices and work space restraints should be considered.  For
example, wax-impregnated cotton inserts may be unsuitable for
high temperature environments due to the softening or melting
of the material; ear muffs may be best for intermittent use
where the individual must go in and out of noise frequently;
ear muffs may not be suited to use with other equipment such
as goggles or respirators; and inserts may be desirable where
use is anticipated in very close quarters such as machine
repair and maintenance might require.

     It has become evident that few devices, if any, will
provide an optimum fit for everyone.  The matter of proper
fit is essential to realizing the attenuation potential of a
device.  Much of the developmental efforts for hearing pro-
tection have been directed to broadening the range of persons
that a particular protector can fit properly.  For example,
the V51-R ear insert was originally manufactured in small,
medium and large sizes.  This was broadened to include extra-
small and extra-large which fit up to 95% of the population.
It was felt that an extra-extra large size would be necessary
to obtain 98% fit.  Another example is the triple-flanged
insert which was first believed to fit everyone by providing
three progressively larger concentric flanges.  It soon be-
came necessary to manufacture three sizes to provide an ade-
quate range of fit.  A final example is the E-A-R expandable
foam insert which is squeezed to a small cylinder, inserted

and allowed to expand in the ear canal.  Even with this mold-
able device it became beneficial to reduce the original
diameter of the foam cylinder to provide improved range of
     In addition to providing a satisfactory fit initially,
the hearing protective device must be able to maintain its
fit during a variety of activities such as talking, chewing,
and head movement.  For inserts this requires adequate depth
of penetration and pressure on the ear canal.  For muffs it
requires flexible joints, proper ear cushions, and adequate
headband tension.
     Fit is less of a problem for ear muff devices, but still
requires special considerations.  First, it is necessary to
cover the entire ear comfortably while allowing a minimum
cirjcumference for the cushion seal.  This minimizes the inter-
ference of physical irregularities.  Next, it is necessary to
provide a loose joint between headband and earcup to accommo-
date the range of skull curvatures encountered.  Finally, the
headband must be adjustable to allow for different sized
heads and ear location.  This is accomplished either by an
adjustable headband or a movable ear cup joint.

     The need for satisfactory comfort is essential if hearing
protectors are to be used.  Obviously, if use of the device
creates greater discomfort than the noise, it will be discarded,
It is certain that no one device will be comfortable to every-
one.  Therefore, it is desirable to be able to select from
different styles.  It is, however, equally certain that some
persons will not find any device comfortable.
     The major cause of discomfort is pressure exerted either
on the ear canal by inserts or the side of the head by muffs.

Unfortunately, pressure is required to create and maintain
the seal so crucial to attenuation.  Thus, a major design
objective is to obtain and maintain the required fit, while
creating the minimum pressure.  This is accomplished both by
use of soft, pliable materials and through various design
features.  For inserts the sizing is very important and in
muffs the ear cushion is critical.  Some inserts are hermet-
ically sealed and others have multiple soft flanges, along
with various sizes.  Ear muffs use foam, air filled, and
liquid filled cushions for comfort.  Undue pressure may occur
when straight symmetrical inserts are provided for an obliqud,
asymmetrical ear canal.  This emphasizes the need for a cer-
tain minimum number of devices to select from.
     Another factor which is cause for discomfort is the
weight of the device, thus introducing another design re-
straint.  Since attenuation is related to mass and density,
a trade off with weight and effectiveness, and weight and
comfort, is required.

     It is wise to include the care requirements of a device
in the purchase decision.  Factors affecting care, such as
the type of environment, the duration of exposure, the type
of user and available facilities to provide the proper care
should be considered.
     For example, ear muffs may require a closed space for
storage depending upon the environment.  Molded inserts may
need a near-by sink.  If inserts are removed often, a sink
may be necessary very close at hand.  Provisions must be made
to care for hearing protective devices in the necessary man-
ner.  The more convenient it is to provide the necessary
care, the better the care will be.

     Hearing protective devices vary considerably in cost
from a few cents to about $12.00.  The cost must be consid-
ered in the light of other factors.  For example, there is
no need to purchase ear muffs or even pre-molded inserts for
one day's use.  It may not be economical to purchase dispos-
able inserts for repeated daily use.  It may be wise to main-
tain some choice if cost is nearly the same and other factors
are satisfied.  Thus, one might have the choice between pur-
chasing one pair of ear muffs or ten ear inserts.  Personal
preference could then be the determining factor if all else
were equal.
     Cost must also be put in a perspective which considers
and, weights the importance of wearing the device.  Thus, the
lowest cost may not be the best measure, if the cost is not
significant to start with.  It is better to buy a $10.00
device which is used and is effective than to provide a five
dollar or fifty cent device which is not used.

     This factor is primarily a design consideration of the
manufacturer.  Prior to the use of certain materials, tests
are conducted to determine their compatibility with the human
body.  Unfortunately, it is inevitable that a portion of the
population will be particularly sensitive to certain of the
materials used.  In such cases irritation may result, making
it difficult to continue the use of the protector.  Poor
hygiene practice may also cause problems and it is necessary
to distinguish between the possible causes.
     Another problem may arise from the accumulation of ear
wax which may obstruct the insertion of the device resulting
in discomfort and a poor seal.  The ear protector may tend

to push wax inward toward the ear drum, causing additional
     Another consideration is that some individuals have a
boney projection from the external auditory canal.  Unless
the projection is quite large there is usually not a problem
since most devices do not reach that deeply into the auditory
     Finally, more careful consideration needs to be given to
the projection found in front of the external ear called the
tragus.  In many individuals the tragus extends too far back-
wards over the ear canal opening and thereby prevents the
insertion of an insert device to its intended depth.  The
tragus may also produce unequal pressure against the device,
forcing the device backward and outward, displacing it enough
to cause an acoustic leak.

     The ability of a device to maintain its integrity for a
satisfactory period of time is an important consideration
from various viewpoints, such as health protection and eco-
nomics.  Durability refers to the endurance of the other
properties being considered in the section.  It is high-
lighted here because when considering each of the factors .of
selection, attention must be given to the durability of each
attribute.  How long will a device provide the attenuation
needed?  How long will it remain confortable and maintain the
proper fit?  How long will it remain hygienically acceptable?
These are questions which should be asked when purchasing
hearing protective devices.  It is known that these devices
age and deteriorate to varying degrees.  There is very little
information found regarding the useful life of hearing pro-
tective devices.  Different materials will shrink, harden or

become too soiled for use depending upon the environment in
which it is used and also the individual using it.
     Manufacturers can give general guidance, but it is
necessary for the user to be sensitive to changes in hearing
protectors.  At present the useful life is determined by the
materials involved, the use environment, and personal exper-
ience.  Various efforts are underway to develop a field test
to evaluate the practical protection of these devices when
in use.  Such a test will permit the evaluation of reliability
and could shed some light on durability.
     A summary of some of the advantages and disadvantages of
the currently available hearing protectors is as follows:

Insert Type Devices

     o    small and easily carried
     o    can be worn conveniently and effectively with
          other personally worn items
     o    relatively comfortable to wear in hot environments
     o    convenient for use where the head must be maneuv-
          ered in close quarters
     o    the cost of pre-molded inserts is significantly
          less than that of others; though other inserts may
          be comparable to other type protectors

     o    sized inserts require more time and skill for fit-
          ting than muffs
     o    the amount of attenuation provided is more variable
     o    proper hygiene is more difficult when devices must
          be removed and re-inserted .

     o    many inserts are difficult to see from a distance;
          hence, it is difficult to monitor groups using
     o    inserts can be worn only in healthy ear canals and
          even some healthy canals require a period of time
          for acceptance

Muff Type Devices

     o    attenuation is less variable
     o    one size muff accommodates large range of head
          sizes and shapes
     o    relatively large sizes are readily visible at a
          distance; thus, use of these protectors by groups
          is easily monitored
     o    muffs are more convenient when use is intermittent
     o    muffs can be worn in spite of minor ear infections
     o    muffs are not lost as easily as inserts

     o    muffs are uncomfortable in hot and/or humid envir-
     o    muffs are not easily carried or stored
     o    muffs are not as compatible with other personally
          worn items
     o    headband spring force may diminish from use or
          from deliberate actions and reduce the protection
     o    muffs may be awkward when used in close quarters
     o    muffs are more expensive than most insert devices

Ear Cap Devices
     These devices which attempt to seal the outer edge of
the ear canal, fill the middle ground between inserts and
muffs.  As such, they reduce the disadvantages of each while
preserving many of the advantages.


     Since hearing protective devices are used to prevent
noise from entering the ear, it follows that the ability to
attenuate noise is the single most important parameter.  All
of the factors of selection may be traded off against one
another, but the amount of hearing protection required and
the ability of a device to provide the necessary attenuation
must be firmly established first.
     Noise may reach the inner ears of persons wearing pro-
tectors by four different pathways.  These are:  (1) by pass-
ing through bone and tissue around the protector; (2) by
causing vibration of the protector which in turn generates
sound into the internal ear canal; (3) by passing through
leaks in the protector; and (4) by passing through leaks
around the protector.  These pathways are illustrated in
Figure 1.  Even if the device permits no acoustical  leaks
through or around it, some noise will reach the inner ear by
the first two of these pathways if the levels are sufficiently
high.  The practical limits set by the bone and tissue conduc-
tion threshold and the vibration of the protector vary con-
siderably with the design of the device and the individual's
physical make-up.  However, approximate limits for inserts
and muffs have been determined and are illustrated in Figure 2,

                                                                                                               Cartilage and Flesh
                                   Bone and
                                   Tissue Conduction
                                                                               (c)  Schematic Representation
                                         Figure 1. Noise Pathways  to the Inner Ear.


                                     Limitation Set By
                                     Earplug Vibration
                                          Range of Bone and
                                          Tissue Conduction
Limitation Set By
Earmuff Vibration

                                Frequency in Cycles Per Second
Figure  2.    Practical  Protection Limits  for Plugs and Muffs

     In order to approach these practical limits of
attenuation, the hearing protector must minimize losses due
to acoustical leaks. The following design criteria should
be useful in accomplishing this goal:
     1.   Hearing protectors should be made of imperforate
          material. If it is possible for air to pass freely
          through a material, noise will also be able to
          pass with little attenuation.
     2.   Protectors should be designed to conform readily
          to the head or ear canal configuration so that an
          efficient acoustic seal can be achieved and the
          device worn with reasonable comfort.
     3.   Protectors should have a support means or a seal
          compliance that will minimize protector vibration.
     It is interesting to note how these design criteria
have been applied to the current generation of hearing pro-
tective devices. Also of interest is the tradeoff of selec-
tion factors necessarily encountered in hearing protector
design.  A brief discussion of such observations follows.
     Ear muffs use a stiff plastic cup to reduce transmission
of sound. The greater the mass (hence weight) the greater
the attenuation for a given material. Weight is a comfort
factor and, therefore, a tradeoff arises.  Similarly, the
greater the headband tension, the better the acoustic seal
with the head.  Tension is also a comfort factor and again
a tradeoff exists.  The need to accommodate a.wide range of
head size has led to the use of a loose joint where the ear
cup meets the headband.  This permits less headband tension
to obtain a satisfactory seal for more head shapes.  The
need to fasten the ear cups to the headband has required
special attention to obtain an airtight fastening system.

A suitable material was needed for the ear cushions to allow
durability, comfort, cleansibility and a good seal.  All of
these qualities cannot be expected to be optimized in any
one material; hence, more tradeoffs.  The ear cup volume
necessary for good low frequency attenuation is restricted
by practical size limitations of the device for comfort and
     A similar situation exists for insert devices.  Here
comfort and fitability are even more sensitive.  A plug must
be soft and pliable for comfort and fit, yet firm and dense
for good transmission loss.  Materials of relatively low
density have been used with good attenuation results, however,
They must fit tightly to avoid vibration of the device and
subsequent noise generation.

     A variety of different methods have been experimented
with to yield meaningful information regarding the attenua-
tion capability of hearing protectors.  These techniques may
be classified as either subjective or physical.  Subjective
methods measure one of an individual's psycho-acoustical
responses with and without the protector in place.  Physical
methods are those in which the sound pressure level inside
and outside the protectors are measured directly.  A brief
discussion of various methods reported in the literature is
appropriate, but closer attention will be given to 'the sub-
jective method which has been widely adopted as the standard
method.  This method, entitled "Measurement of Real-Ear
Attenuation of Ear Protectors at Threshold," has been used
extensively to report the performance of most currently
available devices.

Subjective Methods
     The threshold shift method of evaluating attenuation
determines a subject's threshold of hearing with and without
a protector.  This was the first psychoacoustic method used.
The threshold shift is determined for both ears simultane-
ously using pure tones in a free or nearly free sound field.
Narrow and broad band noise have also been used.  Broad band
stimuli were given little attention due to 'the frequency
dependent nature of attenuations.  A Japanese standard
(JISB9904-1598)  describes a threshold shift method testing
one ear at a time.  It requires the subject to press the
side of his head against a foam rubber bordered hole in a
loudspeaker box, in which the stimulus is presented.
     A masked threshold shift method has been used.  An
active earphone is inserted under an earmuff and the thresh-
old for a stimulus presented by the earphone is determined
with and without high ambient noise present.  The difference
in the threshold provides a measure of the amount of masking
noise excluded by the ear muff.
     Another method called loudness balance has been
reported.  The procedure requires the subject to match the
loudness of an auditory stimulus perceived while wearing a
hearing protector with the same stimulus after removing the
protector.  This method has been conducted with pure tones
in a free field and half-octave band noise in a diffuse
     The difference in sound pressure level necessary to
elicit action of an individual's acoustic reflex with and
without hearing protectors has been measured.  Also the
difference in temporary threshold shift  (TTS) observed with
and without protectors in continuous and impulsive noise
has been measured as an indicator of performance.

     Articulation or intelligibility testing in quiet, with
and without hearing protectors, provides an indication.of
the degradation of speech communication by protectors.  How-
ever, it has been found that in a relatively high noise
field, communication is enhanced with the use of hearing
protectors.  This is accounted for because the attenuation
maintains nearly the same speech to noise ratio while bring-
ing the levels out of the range of auditory distortion.
     The last subjective method to be mentioned here is to
simply allow an individual to wear a variety of different
devices and ask him to choose the best one.  Experiments of
this nature have shown that unless the attenuation of the
protectors differs considerably, effectiveness ranking by
the subjects is not useful.

Physical Methods
     Direct physical measurement of hearing protector
attenuation is attractive because of the relative simplicity
and objectivity as compared to subjective measures.  Unfor-
tunately, modeling and producing a test fixture which repro-
duces the acoustical response of a human head or ear through-
out the audible frequency range is a difficult task.
     At present, a standard method for ear muff measurements
exists using a "dummy" head fixture.  The method is intended
to supplement the subjective test for such purposes as pro-
duct design and quality control.
     A variety of experiments have been reported using
different means to simulate human conditions.  These include
artificial ears and heads.  One experiment uses ear canals
from human cadavers as test devices.  Another system uses a
small microphone inserted under or through an ear muff.
This permits sound pressure level measurements as the

protector is worn by human subjects, thus measuring the
attenuation directly.  This method has produced good agree-
ment with subjective measures at mid and high frequencies,
but low frequency results are 3 to 10 decibels off.  One
difficulty is that the placement of the monitoring microphone
is crucial.  Displacements as small as one millimeter may
cause changes in measured sound pressure level of six decibels
or more at high frequencies.

     The need for a standardized methodology for determining
and reporting hearing protector attenuation is apparent when
the variety and sensitivity of these measurements are con-
sidered.  This was first done in 1957 when the American
National Standards Institute (ANSI) published standard
Z24.22-1957, "American Standard Method for the Measurement
of the Real-Ear Attenuation of Ear Protectors at Threshold."
As mentioned in the Foreword to this standard, it was orig-
inally intended to establish psychological and physical
procedures for evaluating hearing protectors.  However, the
scope was reduced to a specification of procedures for eval-
uating real-ear attenuation on the basis of auditory thresh-
olds on human observers.  It is further stated that the
wirting group is aware of the simplicity of purely physical
methods, but feels the questionable comparison to human
subjective results is overriding.  Finally, the need for
continued efforts in the field and subsequent revisions to
the standard are recognized and recommended.
     Standardization of this methodology by ANSI indicates
that at that time the subjective threshold shift method was
the only technique which received sufficient unanimity of
expert opinion to be standardized.  The standard specified

that the thresholds of at least ten randomly selected, normal
hearing subjects be measured with, and without the protector
worn.  This was to be done on no less than three separate
occasions, for each individual at a minimum of nine pure-
tone test frequencies (125, 250, 500, 1000, 2000, 3000, 4000,
6000, and 8000).  The difference between the thresholds with
and without protectors at each test frequency is reported as
the protectors' attenuation characteristics.
     This standard, Z24.22-1957, has been used extensively
in determining and reporting attenuation performance.  A
number of shortcomings of this procedure have been realized
and have led to the revision of this standard in 1975.
Before discussing the recently published revision, it is
worthwhile noting these limitations.  First, pure-tone
signals are not characteristic of the broad band noises
which are normally encountered.  Second, the use of threshold-
level test tones may not accurately represent performance of
protectors in high level noise.  Third, test tones are intro-
duced only from the front position.  Attenuation has been
observed to vary up to 10 dB with the angle of incidence.
Finally, the time required to perform this test procedure
is very lengthy and the test room requirements are strict.
     Recognizing the impact of these factors, the U.S.
Department of Health, Education and Welfare supported
research which was intended to serve as a foundation for
revisions to this standard.  The most important conclusion
of this research was that ". . . . measurement of hearing
protector noise attenuation by a threshold shift technique
in diffuse sound field using one-third octave bands of noise
as stimuli is a desirable technique and is amenable to atten-
uation standardization.  This technique eliminates the prob-
lems associated with pure tone stimuli and a fixed angle of

incidence and also more closely approximates the noise
exposure conditions in which hearing protectors are usually
     The revised standard, then, which is based on research
performed at the  Pennsylvania State University • and supported by
HEW, was published by the Acoustical Society of America in
mid 1975.  It is officially known as ASA STD 1 - 1975 "
"Method for the Measurement of Real-Ear Protection of Hearing
Protectors and Physical Attenuation of Earmuffs."      :
     The primary improvements over the previous standard are
the use of a diffuse sound field and one third-octave band
test tones.  The diffuse field eliminates the effect of angle
of incidence since diffuse sound impinges randomly from all
directions.  The diffuse field also facilitates creation of
the proper test conditions since a free field is more diffi-
cult and costly to produce.  The use of third-octave band
test tones is more realistic than use of pure tones and
enhances reproducibility of results by reducing possible
variations due to excitation of resonances in the.devices.
Small differences in the absolute frequency of pure tones
may cause disproportionately larger differences in the
measured attenuation between investigations.
     In addition to these revisions to the subjective thresh-
old methodology, a supplemental physical test for ear muff
devices is included in the standard.  A "dummy head" with an
artificial flesh material is specified for obtaining attenu-
ation measurements.  As stated in the Foreword to the stan-
dard, "the physical measurement method is intended for pro-
duction test and engineering design. . . . it is not suitable
for earplug testing."

      Most hearing protector manufacturers  have determined
 the  attenuation capability  of  their devices  in accordance
 with ANSI Z22.54-1957  and report the attenuation value at
 each discrete fest frequency.   Some manufacturers have
 obtained data using the ASA STD 1-1975 methodology,  but do
 not  report it because  the results generally  indicate some-
 what less attenuation  than  the Z22.54-1957 test.  Performance
 testing is usually conducted by an independent testing lab-
 oratory so as to insure unbiased evaluations.
      A report 'by the National  Institute for  Occupational
 Safety and Health, HEW Publication No. (NIOSH)  76-120, con-
 tains attenuation data compiled for a wide variety of hearing
 protectors.   These data was  collected by NIOSH in response to
 a letter survey of manufacturers.  It does not claim to be
 complete nor  does it endorse the data submitted by the manu-
 facturers. The compiled data  includes the standard deviation
 of the measurements at each frequency, thereby providing an
 indication of the variability  in performance to be expected.
      The data represents the current state-of-the-art of
 hearing protector attenuation.  The range  on attenuation at
'the  test frequencies is indicated below.

                          Table 1
            State of the Art of Hearing Protector
                  Attenuation vs. Frequency
                 125 250 500 1000 2000 3000 4000 6000 8000
 Attenuation (dB)  33 35  37   46   46   48   50   48   52
 Attenuation (dB)   3   4  5   13   22   28   25   27   19

     Wearing hearing protective devices will interfere with
.speech communication in relatively quiet environments. How-
ever, when worn in high level noise  (90-199 dB(A)) hearing
protectors not only do not interfere, but may actually
enhance speech intelligibility for normal ears.  The reason
is that hearing protectors maintain approximately the same
speech to noise ratios, while reducing the absolute levels.
This reduces distortion due to overdriving of the auditory
mechanism.  This may not be the case for individuals who
have hearing impairments, although no studies have been
found to determine the effect of a hearing impairment.
Figure 3 illustrates the effect of hearing protectors on
speech intelligibility in various noise environments.

     The attenuation data obtained from the standardized
threshold shift methodology is very useful performance infor-
mation, provided it is interpreted and applied correctly.
However, it may be difficult for many interested individuals
to relate octave band attenuation values to the commonly
used A-weighted sound pressure level noise descriptor.  In
other words, most noise levels and current standards are
expressed in A-weighted decibels, a unit which weighs each
octave band empirically according to human response and then
sums these values.  This is the most common notation and is
symbolically represented as "dB(A)."
     Recognition of this difficulty in relating the standard-
ized attenuation data to practical, everyday noise measure-
ments, has led to the development of various techniques which
provide an estimate of the dB(A) noise reduction from the



                  Earplugs (V-51R)
             15  25  35  45   55   65  75   85   95   105  115

                   Level of Received Speech in dB
Figure  3.   Relation  between speech discrimination and  signal

(speech)  level with  and without earplugs  (V-51R).  Parameter
is level  of masking  noise.  [2]

octave band attenuation values.  These techniques are
similar to one another and, generally, trade off accuracy
for simplicity.  The primary difficulty in estimating dB(A)
reduction is due to the fact that the performance of hearing
protective devices depends upon the frequency spectrum of
the noise.  Consequently, it is common for a single device
to provide substantially different amounts of attenuation
for different noise fields when expressed in terms dB(A).
Therefore, specifying a constant value of expected dB(A)
attenuation is virtually impossible.  Also, there is a
significant variation in hearing protector performance
observed from individual to individual.  This variation is
expressed statistically as the "standard deviation" calcu-
lated at each frequency from the 30 measurements required
by the standard procedure.
     There are three basic techniques for relating octave
band attenuation to dB(A) attenuation.  These are described
below qualitatively by listing the major steps in the  pro-
cedure.  The distinction between the techniques lies in
what data is required to apply the technique and the accuracy
of the estimated attenuation value obtained.

Method One
Data Required:   Octave band noise levels at 125, 250, 500,
                 1000, 2000, 4000, and 800 hertz  (Hz) the
                 dB(A) noise level
                 Hearing protector mean attenuation data at
                 125, 250, 400, 1000, 2000, 3000, 4000,
                 6000, 8000 Hz.
Comments:        Most precise method
                 Attenuation value will vary for different
                 noises but not for different levels of the
                 same noise

Apply the A-weighting to the sound pressure
level at each frequency to yield A-weighted
octave band data

Logarithmically sum A-weighted octave band
sound levels

Adjust the hearing protector attenuation
data for statistical variation by subtract-
ing two standard deviations at each

Subtract the adjusted attenuation values
from the A-weighted octave band sound

Logarithmically sum the values from the
previous step to yield the A-weighted sound
level under the hearing protector

Subtract the calculated level under the
protector from the A-weighted noise levels
to obtain the dB(A) attenuation capability
of the hearing protective device
Method Two
Data Required:
A-weighted sound level of the noise

C-weighted sound level of the noise

Hearing protector mean attenuation data at
125, 250, 500, 1000, 2000, 3000, 4000,
6000, 8000 Hz

Second most precise of the three techniques

Requires that the reduction factor be sub-
tracted from the C-weighted sound level to
obtain A-weighted sound level entering the

Reduction factor is constant although
C-weighted sound level values change with
differing noise spectrums

Apply A-weighting to an assumed "pink"
noise spectrum of 100 dB in each octave

Adjust heaing protector mean attenuation
data for statistical variation by subtract-
ing two standard deviations at each

Subtract the adjusted attenuation values
from the A-weighted octave band sound

Logarithmically sum the values from the
previous step to obtain the A-weighted
sound level under the hearing protector

Add 3 dB(A) to the level under the
protector to correct for actual noise
spectrum variations

Subtract this value from the C-weighted
value of the pink noise spectrum to obtain
the reduction factor
Method Three
Data Required:
A-weighted sound level of the noise

Hearing protector mean attenuation data

Least precise of the three methods

Requires large correction for.noise spectrum

Reduction factor is constant but must be
used with caution

Apply A-weighting to assumed "pink" noise

Logarithmically sum octave bands

Adjust hearing protector mean attenuation
values by subtracting two standard
                             35 .

                 Subtract adjusted attenuation values from
                 A-weighted pink noise spectrum
                 Add empirically determined .value of
                 8.5 dB(A) to previous value to adjust for
              ;   spectrum uncertainty, to obtain estimated
              :   sound level under the protector
              i   Subtract the value under the protector
                 from A-weighted sound level of the pink
                 noise to obtain reduction factor
     It should apparent that the three methods presented
exemplify the trade off between the complexity of the infor-
mation required and the accuracy of the results obtained.
Method One is the most accurate and, therefore, the most
desirable to apply when possible.  It requires the most
complete information about the noise spectrum which necessi-
tates .the use of a Type 1 sound level meter with octave
band filtering capability.  Method Two involves only the
magnitude of the A and C-weighted sound levels.  A reduction
factor is obtained which when subtracted from the C-weighted
sound level of the noise yields the A-weighted sound level
entering the ear.  This method was developed empirically and
requires a 3 dB correction for noise spectrum uncertainty.
Method Three requires only the A-weighted sound level, but
necessitates an 8.5 dB correction for spectrum uncertainties,
It provides a factor which when subtracted from the
A-weighted sound level of the noise yeilds the A-weighted
sound level entering the ear.
     All three methods utilize the mean attenuation data
determined by the ASA STD 1-1975 procedure along with the
standard deviation.  In each case the mean attenuation
values are adjusted by two standard deviations for statistic
cal variation to insure that 95% of the population realize
at least that amount of noise attenuation.  Each method

requires the ability to logarithmically sum decibel values
which is more complex than basic arithmetic calculations.

                         SECTION V

     The Agency has experienced difficulty in obtaining
quantitative information regarding the hearing protector
industry.  The total response to the advanced Notice of
Proposed Rulemaking included ten submissions to the docket.
None of the responses addressed in detail the inquiry
requesting information describing the hearing protector
industry.  The response submitted by £he Industrial Safety
Equipment Association, Inc.  (ISEA)  states that there are
presently 25-30 major manufacturers.  The 17 members of ISEA
are estimated to account for 80 percent of the sales volume.
Their specific response to the ANPRM inquiry was, "The mar-
keting information requested is not available in any form
that we know of."  The National Institute for Occupational
Safety and Health (NIOSH)  responded, "We have no information
on this item."
     A certain amount of qualitative information has been
gathered, however, from ISEA, NIOSH, and others active in
the field of hearing protectors.  This information is pre-
sented here.  In order to obtain further, more detailed
information, EPA has recently distributed letter requests
to nine companies selected from a list of manufacturers
compiled by NIOSH.  Any additional information available
from readers of this document would be welcomed by the
     The hearing protector industry is comprised of 25-30
major manufacturers as estimated by ISEA.  However, there

are numerous small manufacturers, as well as many individuals
who produce custom molded ear plugs.  To further complicate
the picture, there are various companies who distribute
hearing protectors under their own trade name which are
manufactured by another company.  This means the same device
is marketed under different trade names and therefore, it is
difficult to identify all unique devices.  Also, a manufac-
turer of, let us say, ear muffs may market someone else's
plugs so that they have a complete line of hearing protectors
to offer.  The list compiled by NIOSH includes 40 "manufac-
turers or suppliers."  The list of 17 ISEA members includes
five companies not appearing on the NIOSH list.  That implies
45 "manufacturers or suppliers."  It is not proper to consider
these lists complete; only that they represent the majority
of the hearing protector industry.  Considering the foregoing,
it seems safe to estimate that approximately 30 major manu-
facturers produce most of the hearing protectors marketed
     There have been no estimates made of the number of
hearing protectors manufactured.  Various sources have been
consulted including the Department of Commerce which period-
ically conducts a census of all products manufactured.
Unfortunately, hearing protectors are apparently grouped
under "miscellaneous" in the "personal protective equipment"
category.  This information is included in EPA's letter-
request, in hopes of compiling some rather broad estimates
of the types and quantities of each of these devices
     The current consuming market of hearing protectors is
the military/industrial segment 'of the country.  It is here
where large quantities of hearing protectors are used to
protect individuals from noise levels which can damage

hearing permanently.  Most of these purchasers are reached
either by the manufacturers themselves or by distributors
of personal safety equipment.
     Although it is growing, the present public consumption
of hearing protectors is relatively small.  Very few hearing
protectors are found in common retail establishments.  Where
they are found, the choice is very limited.  Most of those
found are either the malleable inserts or the ear muffs,
since these devices minimize problems encountered withjfit.
As environmental noise levels continue to intrude and the
public becomes more aware, citizen use of hearing protectors
will most likely increase substantially.

                        SECTION VI
                     ECONOMIC ANALYSIS


     1.   Number of tests required beyond present testing
     2.   Preparation of Labeling Verification Reports
     3.   Maintenance of required records
     4.   Compliance planning
     5.   Development and, or revision of product graphics,
          packaging and literature
     6.   Costs of labeling requirements over present
          product labeling.

     1.   Numbers of additional tests required
          a)   Initially
               o    One for each model protector
               o    Three for 3-position earmuffs
          b)   Annually
               o    Assume product changes to 20% of models
     2.   Amount of Compliance Audit Testing
               o    No fixed amount, may be very minimal
               o    Assume average of one additional test
                    per year
     3.   Cost per test
               o    $1,500 - $2,000 per test per headband

4.   Preparation of Labeling Verification Reports
          o    Technical   2-weeks     $1,000
          o    Clerical    2-weeks        400
          o    Reproduction/Printing      100
               (Assumed average costs, actual costs
               will vary with numbers of protectors

1.   Ear Inserts
          o    Premolded                35
          o    Moldable                 13
          o    Non-Linear                3
2.   Ear Muffs
          o    One-position             58
          o    Three-position
               18 x (3)                 54
3.   Ear Caps
          o    One-position              2
          o    Two-position 1 x  (2)      2
          o    Three-position 1 x  (3)    3_
               TOTAL MODELS  170

     (ONE-TIME)  •
               o    From     170 models x $1,500 per model
                             (testing) = $255,000
               o    To       170 models x $2,000 per model
                             (testing) = $340,000
          $255,000 - $340,000 One-time Initial Testing Costs

               o    Assume that each manufacturer will be
                    required to perform one additional test
                    each year on the average.
               o    No. of Manufacturers = Approximately 41
               o    Costs
                    From     41 x $1,500 per test = $61,500
                    To       41 x $2,000 per test = $82,000
          $61,500 - $82,000 Annual Costs for Compliance
                            Audit Testing •

               o    Assume that 20% of models  need  reverifi-
                    cation or are new models.
               o    Costs
                    170 models x  .20  = 34
                    From     34 models x $1,500 per model
                              (testing) = $68,000
          $51,000 - $68,000 Annual Cost of  Labeling
                            Verification Testing

     1.   This 'includes preparation of new or revised product
          graphics, packaging and literature.
     2.   Manufacturer Survey Summary
               8 Replies
               o    Minimal Costs           4
               o    Not Available           2
               o    $0.10 per unit          1
                    (Rounded devices)
               o    $1,000                  1
                    (Typesetting & Artwork
     3.   Costs
               o    Assume 41 manufacturers
               o    Assume cost for revised artwork and
                    graphics of $3,000 per manufacturer.
               o    $3,000 x 41 = $123,000
          $123,000 One-Time Direct Labeling Costs

     1.   Includes
               o    Development of Compliance Plan
               o    Preparation of Labeling Verification Plan
               o    Maintenance of Records
               o    Administrative Costs of Compliance Audit
     2.   Assume the following personnel requirements
               o    1 week - senior-level at 50,000 per year
               o    2 weeks -mid-level at 30,000 per year
               o    2 weeks - technician/clerical at 10,000
                    per year

     3.   Costs                    v
               o    1/50 x 50,000 per year  =  $$1,000
               o    2/50 x 30,000 per year  =    1,200
               o    Cost of Preparation of
                    Labeling Verification
                    Report (3 (4))           =    1,500
               o    $3,700 x 41 manufacturers = $151,700
          $151,700  Annual Administrative Costs

     1.   Initial Costs (One-Time)
          a)    Label Verification Testing   $255,000 - $340,000
          b.    Labeling Preparation         $123,000 - $123,000
          Total Initial Costs
               $378,000 to $463,000
     2.   Annual Costs
          a)    Compliance Audit Testing     $61,500 - $82,000
          b)    Label Verification Testing   $51,500 - $68,000
          c)    Administrative Costs     '   $151,700 - $151,700
          Total Annual Costs
               $264,200 to $301,700

                   SECTION VII

Professor Paul L. Michael, Pennsylvania State University,
     Personal Protective Devices and Hearing Conservation
Donald C. Gasaway, Personal Ear Protection, Aeromedical
     Review, USAF School of Aerospace Medicine, August
David F. Bolka, Methods of Evaluating the Noise and Pure
     Tone Attenuation of Hearing Protectors, Thesis
     Abstract, Pennsylvania State University, December
P.S. Veneklasen, Methods of Noise Control:Personal Pro-
     tection, Noise Control, ]L, 29-33, September 1955.
U.S. Department of Health, Education, and Welfare,
     National Institute for Occupational Safety and
     Health, HEW (NIOSH) Pub. No. 76-120.
Acoustical Society of America, Standard, ASA Std 1-1975,
     Method for the Measurement of Real Ear Protection
     of Hearing Protectors and Physical Attenuation of