SECTION 8: What OSHA Expects
From You
By now nearly everyone agrees that hearing loss can be caused by exposures
to loud noises. Obviously, the louder the noise the shorter the exposure
needed to cause hearing loss: So the Department of Labor, through OSHA, has sought tp provide protection to workers whose jobs involve exposure to
high noise levels.
Setting limits on occupational noise exposure, however, has proven a
controversial and difficult task, and considerable give-and-take between
labor and industry has occurred. As a result, today's rules governing
occupational noise exposure have grown more and more complex. What follows
is a summary of the rules you should be concerned with as a safety officer.
Department Of Labor Occupational Noise Standards
These rules were adopted in 1971 and still form the core of the federal
occupational noise control effort. In essence, they state that if employees
are exposed to noise levels that exceed those specified in the following
table, a noise control program must be initiated. In essence this means
that the employer must work to reduce plant noise exposures by quieting
plant machinery or reducing the amount of time workers actually spend in
noisy environments. (This is known as an "administrative and engineering
controls" program.) On the top of the following page you will find OSHA's
limits for occupational noise exposure:
Permissible Noise Exposures
Daily Exposure (hours) | Sound Level (dBA) |
8 | 90 |
6 | 92 |
4 | 95 |
3 | 97 |
2 | 100 |
1 1/2 | 102 |
1 | 105 |
1/2 | 110 |
1/4 or less | 115 |
When using the preceding table, remember that these are total daily
exposures--if employees receive only brief exposures, the exposure times
should be added up over the course of the day and compared with the
permitted levels. Also remember that exposure to extremely brief, sharp
noises (called "impulsive" or "impact" noises") of over 140 dB peak sound
pressure levels in intensity is also prohibited.
Hearing Conversation Amendment
This amendment, adopted in 1981 and finalized in 1983, toughened the rule
adopted in 1971: In addition to the 1981 rule, it required that if
employees are exposed to an 8-hour time weighted average of over 85 dBA, a
hearing conservation program must be put into effect. (What a hearing
conservation program involves will be explained below.)
However, when computing a time weighted average for the purposes of
establishing a hearing conservation program, the law also specified that all
noises above 80 dBA must be taken into account. The reasoning behind this
was that even though a hearing conservation program is not triggered until a
time-weighted average of 85 dBA is reached, noises between 80 and 85 dBA in
intensity should also be considered when computing this average because
research has shown that long-term exposures at this level can also
contribute to hearing loss.
This is a very important aspect of the law, as well as the most confusing,
and it bears repeating: An engineering controls program is triggered when
employee exposures exceed a time-weighted average of 90 dBA, and only noise above 90 dBA should be taken into account when computing a time-weighted average for this purpose. However, a hearing conservation program
is triggered when employee exposures reach a time-weighted average of 85
dBA, but noises as low as 80 dBA should be taken into account for this
computation.
The computer program used to calculate time-weighted averages from the
data stored by the SNX-85C takes these rules into account so you don't have
to worry about them. Your SNX-85 data sheets also take these rules into
account on the engineering controls data sheet by multiplying all exposures
below 90 dBA by zero so they drop out of the calculation. On the hearing
conservation analysis data sheet, on the other hand, all levels between 80
and 90 dBA are included in the calculation.
Hearing Conservation Program
This program is generally required for employees who are exposed to a
time-weighted average of over 85dBA, calculated as explained in the
preceding section. Here's a brief outline of what such a program includes:
- Employees affected shall have their hearing acuity evaluated by an
approved professional. The test used to establish hearing acuity is known
as an audiogram, and every year after this first or "baseline" audiogram is
established, another audiogram should be taken for affected employees to
determine whether any hearing loss has taken place in the interim.
Employees must be informed of the results of these hearing tests.
- A variety of hearing protectors must be available to employees in the
hearing conservation program. These employees must wear hearing protection
only if they are exposed to a time-weighted average of 90 dBA or more, but
they may choose which kind of protector they will wear.
- Employees in the hearing conservation program must also be informed of
the effects of noise on hearing, the use and protection afforded by hearing
protection, and the purpose of the annual hearing tests they are required to
take.
- Employers must maintain careful records documenting employee noise
exposures, hearing testing, and the calibration of instruments used to
measure noise and test hearing. Hearing tests shall also be given in rooms
where background noise will not interfere with the tests.