Hearing
Protection
The Safety Source
offers a variety of Hearing Protection products, you may select from
the list below or from the left hand sidebar.
 
Hearing
Protection Selection Guide
Types of Hearing
Protectors
There are three types
of hearing protectors generally used in industry, Argus has provided a
selection from the major manufacturers.
Ear Muffs
Design to fit around the head using a band, noise-attenuating cups with
soft cushions surround the outer ear to seal out noise. Most workers can
use the same size ear muffs; which usually have three different band positions:
over-the-head, behind-the-neck, and under-the-chin. Many ear muffs have
all three positions available through rotating headbands (the position
worn may have an effect on the muffs' noise attenuation, indicated by
the NPR). Most models are available as hard-hat mountable units, some
may require adapters.
Applications requiring
frequent removal of hearing protection are well suited to ear muffs. Ear
muffs when well-cared-for can last for many years; ear cushions and other
wearable parts should be replaced often.
Ear Plugs
Designed to fit snugly into the ear canal, ear plugs are made of a soft,
pliable material to seal out unwanted noise. They are the least expensive
type of hearing protection and can be purchased with or without attached
cords. Attached cords will prevent accidental loss; cords also stand out
so supervisors can easily verify compliance. Usually the molded foam style
plugs are categorized as disposable (good for several usages); while the
plastic style are more durable and can be used for much longer periods
of time.
Ear Bands
These semi-aural devices are fitted with small pods made of a soft material
or flexible tips that seal off the ear canal entrances. Ear bands only
require a minimal insertion to be effective. The band itself, usually
made of plastic, is designed to be worn under the chin or behind the neck.
Ear bands are easy to keep track of because of higher visibility, compliance
is also easier to verify for this same reason. With easy storage around
the neck, they are well suited to applications that require repeated on-and-off
use.
OSHA’s
Hearing Conservation Requirements
Whenever feasible,
employers are required to reduce the noise at the source through engineering
solutions. When this is not possible or economically feasible it is acceptable
to use hearing protection as a temporary solution. The term hearing conservation
as defined by OSHA includes the following aspects, which the employer
is responsible to carry out:
- Monitoring
of the noise environment. If the TWA (Time Weighted Average)
noise level is exceeding 85 dB(A), a hearing conservation program is
required.
- Selecting
hearing protection devices appropriate for the environment
or environments at hand. Several different types of hearing protectors
are required to be offered to the employees, in order to introduce a
level of personal choice. The employer is responsible to pay for the
original equipment as well as replacements. The employees are required
to use the hearing protection, and the employer is responsible for the
enforcement.
- Training
and educating employees in the proper use of hearing protection,
the importance of full time use of hearing protectors when working in
a noisy environment. Education and training is considered an essential
and ongoing activity.
- Establishing
a baseline audio gram for each noise exposed employee, and
annual hearing tests thereafter in order to monitor the hearing health
of the employees. Have the audio grams evaluated by an audiologist or
physician.
- Take corrective
action when it is concluded that a noise induced hearing damage
is occurring. Corrective action can entail further education and training
in the use and importance of full time use of hearing protection. Seeking
the use of hearing protectors better suited to the environment and the
individual. Using, what is called administrative controls, which simply
means to reduce the exposure time for the employee in question. If these
efforts fail, an employee may be transferred to a quieter job.
The above summary
of OSHA’s hearing conservation requirements is not intended to be
complete. The
complete regulation (29CFR-1910.95) is available on the internet.
| OSHA’s
Permissible Noise Exposure |
90
dB |
8.0
hours |
92
dB |
6.0
hours |
95
dB |
4.0
hours |
97
dB |
3.0
hours |
100
dB |
2.0
hours |
102
dB |
1.5
hours |
105
dB |
1.0
hours |
110
dB |
30
minutes |
115
dB |
15
minutes |
What is NRR
(Noise Reduction Rating)?
It is an attempt to
summarize a hearing protectors performance in a simple manner, by processing
all the test data in accordance with an established formula. The rating
is widely used and poorly understood. It gives very high weighing to the
low frequency attenuation, while high frequency performance is not given
the same consideration.
The (Noise
Reduction Rating) Formula
The NRR is a single
number rating which is required by law to be shown on the label of each
hearing protector sold in the United States. The NRR is specified by 40
CFR code of Federal Regulations, Part 211, Product Noise Labeling, Subpart
B - Hearing Protection Devises. It (the NRR) is independent of the noise
spectrum in which it is applied.
The values of sound
attenuation used for calculation of the NRR are determined in accordance
with ANSI S3.19-1974, "American National Standard for the Measurement
of Real-Ear Hearing Protector Attenuation and Physical Attenuation of
Earmuffs." The NRR calculation assumes a pink noise with octave-band
levels of 100dB. Thereafter various correction factors for C-weighting
scale and A-weighting scale are introduced. The octave-band noise levels
are logarithmically summed to obtain the overall sound level in dB(C)
and dB(A). The NRR is computed by subtracting 3 dB from the difference
between the unprotected C-weighted and the protected A-weighted levels
at the ear.
How to use
the NRR
When the dB(C) noise level is known, you don‘t have to adjust the
NRR:
Noise level at ear: dB(C) - NRR =< 90 dB (*)
When the noise level is known in dB(A) the NRR must be reduced by 7 dB:
Noise level at ear: dB(A) - [NRR –7] =< 90 dB (*)
(*) If a threshold shift (hearing damage) exists the noise level at the
ear must be 85 dB or less.
Overprotection can be a problem!
Selecting a high NRR hearing protector for an environment where only good
high frequency attenuation is needed, will lead to unnecessary insulation
and communications difficulties.
Click
here to download a NIOSH document showing how NRR, SNR and HML are
calculated.
Conflicting
Information about How to Use the NRR
Do you know how
to use the NRR values that are required on the packaging of all hearing
protection devices sold in the United States? If you do, you are one of
a kind!
EPA Requirement:
The only law (passed by the U.S. Congress) regulating how to use the NRR,
is actually the EPA labeling regulation, dating back to 1981. This law
directs the user to deduct the NRR from the noise level at hand, in order
to get the noise level at the ear. That is pretty straightforward: Noise
level [98 dB] minus Hearing Protector NRR [25 dB] = Noise at the Ear,
73 dB.
OSHA’s
Field Manual: Although OSHA has no legislative authority, the
agency has in its field manual directed their inspectors to use the following
formula for how to apply the NRR.
- If noise measurements
are made with the dB(A) scale, the following formula applies. (Noise
level [98 dB] minus NRR divided by 2 [25 dB minus 7 dB divided by 2]
= Noise level at ear, 89dB).
- If the noise level
measurements are made with the dB(C) scale, this formula applies. (Noise
level [98 dB] minus NRR divided by two [25 dB divided by 2] = Noise
level at ear, 85.5 dB).
- Although OSHA has
only enforcement authority, their interpretation has held up in court.
OSHA only recommends that the 50% safety factor is applied. Realize
that if a company runs an effective hearing conservation program, they
are not likely to be challenged. An effective hearing conservation program
can be defined as a program that assures that no new permanent and noise
induced hearing losses occur among its employees.
NIOSH, Criteria
for a Recommended Standard, Occupational Noise Exposure, June 1999:
NIOSH recommends that Subject Fit data in accordance with ANSI S12.6-1997
be used. (To our knowledge no U.S. manufacturer has made "Subject
fit" test data available). NIOSH recommends the following de-rating
of hearing protector NRR’s, if subject fit data is not available.
- Earmuffs, Subtract
25% from the manufacturer’s labeled NRR
- Formable earplugs,
Subtract 50% from the manufacturer’s labeled NRR
- All other earplugs,
Subtract 70% from the manufacturer’s labeled NRR
The above de-ratings
apply only when the noise measurement was made with a dB(C) scale. When
only a dB(A) scale measurement is available, the de-rated NRR’s
should be reduced by seven dB. Observe that earmuffs require the lowest
de-rating.
OSHA Web Site,
January 1999: OSHA recommends that manufacturers include a secondary
label for NRR-SF. The SF (Subject Fit) refers to a NRR value achieved
with the new ANSI S12.6-1997, using naïve subjects. Naïve subjects
are defined as individuals having no previous experience in the use of
hearing protection. (Authors comment: The method assures lower NRR’s,
but we are no longer testing hearing protectors, we are testing test subjects.
Better products will not necessarily get higher NRR’s. How about
testing the safety record of new cars by having drivers without license
drive a test course, and the car without dents gets the highest rating).
The naïve subjects are part of the ANSI standard, why OSHA bears
no blame for this situation.
Some Facts
About Noise
Legally noise is exposure
to sounds exceeding an average of 90 dB of noise for eight hours per day.
A TWA (time weighted average) of 90 dB equals the current maximum legal
noise exposure (in the US) for an individual without an existing hearing
damage. The exposure limit for someone with an existing hearing damage
is 85 dB. The exposure level is currently being reviewed and NIOSH is
recommending that the TWA is reduced to 85 dB for all workers.
The legally permissible
noise exposure varies from country to country. U.S. law currently allows
exposure to 90 dB for eight hours. Most countries allow only 85 dB for
an eight hour work day.
Scientifically noise
doubles with every increase of three dB, but U.S. legislation has defined
a five dB doubling for legal purposes. This definition allows more noise
exposure and consequently require less efforts form corporations in regards
to noise abatement and hearing conservation efforts.
You may
also contact Argus for further guidance and selection information.
|
