Geoscience Reference
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1. What is the noise level in each work area?
2. What equipment or process is generating the noise?
3. Which employees are exposed to the noise?
4. How long are they exposed to the noise?
To answer these questions, environmental professionals record their findings as they move from
workstation to workstation, following a logical step-by-step procedure. The first step involves using
the sound level meter set for A-scale slow response mode to measure an entire work area. When
making such measurements, restrict the size of the space being measured to less than 1,000 square
feet. If the maximum sound level does not exceed 80 dBA, it can be assumed that all workers in this
work area are working in an environment with a satisfactory noise level. However, a note of caution
is advised: The key words in the preceding statement are “maximum sound level.” To assure an
accurate measurement, the industrial hygienist must ensure that all “noisemakers” are actually in
operation when measurements are taken. Measuring an entire work area does little good when only
a small percentage of the noisemakers are actually in operation.
The next step depends on the readings recorded when the entire work area was measured.
For example, if the measurements indicate sound levels greater than 80 dBA, then another set of
measurements need to be taken at each worker's workstation. The purpose here, of course, is to
determine two things: which machine or process is making noise above acceptable levels (i.e., >80
dBA), and which workers are exposed to these levels. Remember that the worker who operates the
machine or process might not be the only worker exposed to the noisemaker. You need to inquire
about other workers who might, from time to time, spend time working in or around the machine or
process. Our experience in conducting workstation measurements have shown us noise levels usu-
ally fluctuate. If this is the case, you must record the minimum and maximum noise levels. If you
discover that the noise level is above 90 (dBA) (and it remains above this level), you have found a
noisemaker that exceeds the legal limit (90 dBA). However, if your measurements indicate that the
noise level is never greater than 85 (dBA) (OSHA's action level), the noise exposure can be regarded
as satisfactory.
If workstation measurements indicate readings that exceed the 85-dBA level, you must perform
another step. This step involves determining the length of time of exposure for workers. The easiest,
most practical way to make this determination is to have the worker wear a noise dosimeter, which
records the noise energy to which the worker was exposed during the workshift.
Note:
This parameter assumes that the worker has good hearing acuity with no loss. If the worker
has documented hearing loss, exposure to 95 dBA or higher, without proper hearing protec-
tion, may be unacceptable under any circumstances.
15.7.3.3 Octave-Band Noise Analyzers
Several Type 1 sound level meters (such as the GenRad 1982 and 1983 and the Quest 155) used by
OSHA have built-in octave band analysis capability. These devices can be used to determine the
feasibility of controls for individual noise sources for abatement purposes and to evaluate hearing
protectors. Octave-band analyzers segment noise into its component parts. The octave-band filter
sets provide filters with the following center frequencies: 31.5, 63, 125, 250, 500, 1000, 2000, 4000,
8000, and 16,000 Hz. The special signature of a given noise can be obtained by taking sound level
meter readings at each of these settings (assuming that the noise is fairly constant over time). The
results may indicate those octave-bands that contain the majority of the total radiated sound power.
Octave-band noise analyzers can assist industrial hygienists in determining the adequacy of vari-
ous types of frequency-dependent noise controls. They also can be used to select hearing protectors
because they can measure the amount of attenuation offered by the protectors in the octave-bands
responsible for most of the sound energy in a given situation.
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