Noise Induced Hearing Loss and Its Prevention (cont.)
What are the regulations regarding on-the-job exposure to noise?
Habitual exposure to noise above 85dB will cause a gradual hearing loss in a
significant number of individuals. Moreover, noise greater than 85dB will
accelerate this damage. Accordingly, the U.S. Occupational Safety and Health
Administration (OSHA) has imposed regulations nationwide regarding on-the-job
exposure to noise. For unprotected ears, the allowed exposure time decreases by
one-half for each 5 dB increase in the average noise level. For instance,
exposure is limited to 8 hours at 90 dB, 4 hr at 95 dB, and 2 hr at 100 dB. The
highest permissible noise exposure for the unprotected ear is 115 dB for 15
minutes per day. Any noise above 140 dB is not permitted.
OSHA, in its Hearing Conservation Amendment of 1983, required the institution
of a hearing conservation program in noisy workplaces. Such a program must
include a yearly hearing test for workers exposed to an average of 85 dB or more
of noise during their 8-hour workday. It turns out that approximately 25% of the
American industrial workforce is exposed to level of noise.
Ideally, noisy machinery and work places should be designed to be quieter,
and/or the workers' time in the noise should be reduced. The cost of reducing
noise exposure in these ways, however, is often prohibitive. As an alternative,
individual hearing protectors are required when noise averages more than 90 dB
during an 8-hour day.
When noise measurements indicate that hearing protectors
are needed, the employer must offer at least one type of earplug and one type of
earmuff without cost to employees. If the yearly hearing test reveals a hearing
loss of 10 dB or more in the higher sound frequencies (pitch) in either ear, the
worker must be informed. (The higher frequencies of sound are the most sensitive
to noise damage.) Also, the worker must wear hearing protectors when noise
averages more then 85 dB for an 8-hour day. Greater losses of hearing or the
possibility of ear disease necessitates referral to an ear doctor (otolaryngologist).
Next: How effective are hearing protection devices? »
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