Environmental Engineering Reference
In-Depth Information
1.13.5 hearing Conservation (29 Cfr 1910.95)
A potential hazard of the workplace that is often overlooked is
excessive noise. Noise is usually defined as any unwanted sound. Sound
is caused by rapid fluctuations of air pressure on the eardrum of the
listener. Sound may be unwanted for several reasons, including its con-
tribution to hearing loss, its adverse effects on human physiology, its
interference with normal conversation, or its being just a plain nuisance.
Sound is measured in decibels (dB). The decibel is a dimensionless unit
used to express physical intensity or sound pressure levels. If sound is
intensified by 10 dB, it seems to human hearing as if the sound intensity
has approximately doubled. A reduction by 10 dB makes it seem as if the
intensity has been reduced by half. The reference point for noise level
measurement is 0 dBA, which is the threshold of hearing for a young
child with very good hearing. The threshold of pain for humans is 120
to 125 dBA. The “A” part of dBA is determined by using instruments
used to measure sound levels. The instruments used have a measuring
scale designed to resemble sound that the human ear is sensitive to
(A-weighted sound level).
Noise is a workplace problem. Along with possibly causing perma-
nent or temporary hearing loss, noise also affects the nervous system.
Anyone who has worked at a wastewater treatment plant or pumping sta-
tion knows that the wastewater treatment process produces noise: from
the low barely audible hum of fractional horsepower electric motors to
the din created by 300-horsepower aeration blowers and diesel engines,
the spectrum of noise intensity at a wastewater treatment facility or
pumping station is wide. Hearing loss is a common workplace injury
that is often ignored. As a matter of record, it was not uncommon in the
past for workers to accept partial hearing loss as a cost of working in
a noisy workplace, including a wastewater treatment plant. Times have
changed, however. OSHA recognizes noise for what it really is. Noise is
an occupational hazard that can cause temporary or permanent hearing
loss, stress, and other physical problems.
Because noise is a workplace hazard OSHA has established criteria
for protecting workers' hearing. The main factors related to hearing loss
are intensity, time of duration of exposure, and repeated impact noise.
It is the continuous exposure to high-level noise that must be avoided.
With increased time of exposure, there is a corresponding increase in
harm done.
In order to protect workers and to abide by OSHA requirements,
wastewater facilities need to incorporate a hearing conservation pro-
gram into their overall safety program whenever sounds generated in
the workplace are irritating to workers. When a worker needs to raise
his or her voice to shout to be heard by someone closer than a foot
away, that worker is being exposed to noise levels that are too high.
Moreover, whenever the measured sound levels reach 85 dB or higher
for an 8-hour time period, a hearing conservation program is required
by OSHA.
