Theatre Design & Technology - Fall 1984 - 16

tible to noise damage; the damage is
permanent regardless of degree; and
the deterioration will continue unless
stemmed by a program of noise control
and hearing protection.
Figures 1- 5 represent the deterioration in hearing typical of people exposed to sustained noise at levels above
85 dBA (decibels, "A" weighted). Figure I describes the normal range of
hearing. While much of the power of
speech falls within the range of 500 to
2000 Hz. (Hertz or cycles per second),
frequencies up to 4000 Hz., and in some
cases to 8000 Hz., contribute to speech
intelligibility. Figures 2 through 5 show
the typical progression of hearing loss
leading to greater reductions in speech
intelligibility. While it is rare that a person working in a scene shop would be
exposed to continuous noise levels daily
of 85 dBA or more (levels common in
factories), the potential for hearing
damage still exists.
Other effects of uncontrolled high
noise levels are often irritability, fatigue, carelessness and missed oral instructions-leading to error or physical
harm. Headaches, tension and offhours stress are also common ailments
that the bearer may not directly relate
to the noisy environment in which he
works.
A program of noise control for the
scene shop may include three basic
areas: noise reduction, noise isolation
and personal hearing protection. The
reduction of noise produced by the
equipment in the shop can be accomplished in a number of ways. Good tool
maintenance is an easy first step. Tightening mounting bolts, braces, belts,
guards, casters and other sources of vibration; replacing worn motor brushes;
lubricating moving parts frequently;
and using sharp blades, router bits and
drills are all methods of noise control.
oisy air handlers, dust collection
systems and similar utility apparatus
must also be well maintained and
quieted if possible with sound insulation or vibration dampeners. Other
ambient noise may also be reduced. A
radio set loud enough to be heard over
the normal noise level in the shop adds
2 to 5 dBA or more to the overall noise
level-enough to push the sound level
into the danger range for sustained exposure. Stationary tools such as bench
saws, sanders and lathes may be
mounted on vibration isolators which
14

will limit vibration transmitted to the
floor and re-radiated as noise. Isolators do, however, tend to limit tool
mobility and, as many scene shops are
designed to permit easy movement of
"stationary" bench-type power tools,
the acceptance and use of these devices
may be difficult regardless of their
effectiveness.
While not actually reducing the
noise a machine produces, shielding the
sources of noise from the rest of the
shop may be a real help. Portable
sound control screens six feet high and
made of a heavy intercore of plywood
covered with four inches of fiberglass
and faced with hardware cloth may be

Thealre Design & Technology/USITT/FallI984

Federal Occupational Noise

placed around noisy air compressors,
lathes, sanders and saws. Of course,
care should be taken so that access to
work and ventilation is not inhibited.
Walls and ceilings insulated with sound
absorbent materials such as fiberglass
batts, acoustical tile or Tectum help
limit the buildup of noise within the
work area. Even a few pieces of absorbent material tacked to the wall behind a radial arm saw can be beneficial
to the saw operator as well as other
people in the shop.
The ideal noise reducing scene shop
floor would be decked in small pieces of
continued on page 28 ...

Exposure Regulations *

1
An employer shall administer a continuing, effective hearing
program ... whenever employee noise exposures equal or exceed
an 8-hour Time-Weighted Average (TWA) sound level of 85
decibels.
2

Employers shall make hearing protectors available to all employees exposed to a TWA of 85 decibels or greater at no cost to
the employees.

3
Hearing protectors shall be replaced as necessary.

-----------4----------Employees shall be given the opportunity to select their hearing
protectors.

5
The employer shall provide training in the use and care of all
hearing protectors.

6---------The employer shall ensure proper initial fitting and supervise the
correct use of all hearing protectors.

7----------The employer shall evaluate hearing protector attenuation for
the specific noise environment.

8 ----------Hearing protectors must attenuale employee exposure at least to
a TWA of 90 decibels.
*Federal Register, Vol. 46, No. II, Janl/ary 16, 1981/ Rl/les and Regl/lations

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