CHAPTER 1
SCOPE OF MANUAL
that are needed. The term "engine," as used in the
1-1. Purpose and scope.
manual, may be construed to represent "engine-
This manual provides noise control data and analy-
generator" or "engine-generator set" when used in
sis procedures for design and construction of die-
the larger sense to include both the driver and the
sel, gas, and gas turbine engine facilities at mili-
driven equipment.
tary installations in the continental United States
(CONUS) and for U.S. military facilities around
1-3. Typical problems of uncontrolled noise.
the world. The data and procedures are directed
The noise of a typical engine-driven electric gener-
primarily toward the control of noise from engine-
ator is great enough that it can cause some loss of
driven electric generators but are equally appro-
hearing to personnel working in the same room
priate for any power system using reciprocating or
with the engine, and the noise radiated outdoors by
turbine' engines. This manual applies to all new
an unenclosed engine can be heard a mile away and
construction and to major alterations of existing
can disturb the sleep of people living a half-mile
structures. U.S. military facilities that require
away--if adequate noise control measures are not
higher standards because of special functions or
taken. These two extremes show the range of the
missions are not covered in this manual; criteria
problems that may be encountered with a power
and standards for these exceptions are normally
plant, and they illustrate the range of noise prob-
contained in design directives for the particular fa-
lems covered by this manual. A few specific exam-
cilities. If procedures given in this manual do not
ples are listed and discussed briefly.
provide all the functional and structural needs of a
a. Hearing damage to engine operator. Human
project, recognized construction practices and de-
hearing loss represents the most serious aspect of
sign standards can be used.
the engine noise problem. A power plant operator
1-2. General contents.
who regularly spends 8 hours per day inside an en-
gine room, with no acoustic enclosure and no ear
This manual presents a review of applicable sound-
protection, will experience some degree of noise-
and vibration-level criteria, sound level data for
induced permanent hearing loss over a period of
reciprocating- and turbine-type engines driven by
time in that noise field. Military regulations pro-
gas and liquid fuels, a basic approach for evaluating
hibit such noise exposures, and this manual recom-
an engine noise problem, procedures for controlling
mends separate control rooms for such problems.
engine noise and vibration, and examples that illus-
trate the entire system analysis. The sound level
ty" of the voice is contained in the middle and up-
data quoted in the manual are based on measure-
per frequencies of the total audio range of hearing.
ments of more than 50 diesel and natural gas
When an interfering noise has a frequency spread
reciprocating engines and more than 50 gas turbine
that covers the middle and upper portion of the to-
engines. Almost all of the leading manufacturers
tal audio range, it has the potential of "masking"
are represented in the collection of data. The sound
the speech sounds. If the interfering noise is not
level data given in the manual are 2 dB higher than
very loud, a talker overcomes the masking effect
the average of the measured sound levels in order
by talking louder. If the interfering noise is very
to include engines that are slightly noisier than the
loud, the talker must shout and the listener must
average. This inclusion means that designs based
move closer to hear and understand the spoken
on the data and methods used in the manual will
message. If the interfering noise is too loud, the
provide design `protection for approximately 80 to
voice is not strong enough to overcome the mask-
90 percent of all engines in any random selection.
ing effect-- even at short distances while the
The few remaining engines may have sound levels
speaker is shouting almost into the listener's ear.
of possibly 1 to 5 dB above the values used here.
In such high noise levels, speech communication
Sound power level data are quoted for the engines,
becomes difficult, tiring, and frustrating, and facts
..
but the procedures in the manual show how these
may be distorted when the listener erroneously in-
data are converted to the sound pressure levels
1-1
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