TM 5-805-4/AFJMAN 32-1090
CHAPTER 6
AIRBORNE SOUND CONTROL
6-1. Introduction.
and relatively easy to follow, while designs are
still on paper. Remedial treatments are difficult,
a. This chapter draws together much of the
expensive, time-consuming, and frequently less
factual content of the earlier chapters and presents
effective after the completed designs are fixed in
a systematic approach for evaluating noise data
steel and concrete.
and arriving at design decisions for controlling the
b. In some cases, it is found that the normally
noise of electrical and mechanical equipment
used walls or floors are not adequate, and im-
transmitted between room within a building and
proved versions should be substituted. Three addi-
to other nearby structures. The chapter concludes
tional factors should be considered in an overall
with discussions of the various noise control treat-
acoustic design; these factors are aimed at finding
ments that are practical and available for solution
the best mixture of practicality and total economy.
of equipment noise problems. Almost all sound
One involves the possibility of using noise specifi-
analysis problems can be divided into consider-
cations to limit the amount of noise produced by
ations of the; 1) Source; 2) Path and; 3) Receiver.
Noise and vibration for specific problems may be
noise-dominating equipment, the second involves
reduced by using the following system approach:
use of noise control treatments on particularly
(1) Reduce noise and vibration at the source
noisy equipment, and the third involves building
by using quieter equipment or noise-reducing mod-
layout and equipment arrangement.
ifications.
(1) Use of noise specifications. The use of noise
(2) Prevent noise transmission by using barri-
specifications is presented in chapter 9. It should
ers, and prevent vibration transmission by using
be kept in mind that the noise levels quoted in the
vibration isolators.
manual represent the 80- to go-percentile range of
(3) Relocate the receiver.
the data studied and that it can reasonably be
b. Sources of mechanical equipment sound are
expected that many suppliers of equipment can
provided in appendix C. Considerations for Paths
furnish products that are a few decibels quieter
are given in chapters 3, 4 and 5. Criteria for
than these in the manual, without burdening the
acceptable sound is given in chapter 2. Chapter 7
job with excessive costs. Therefore, when it be-
provides a similar discussion for sound transmitted
comes apparent that one or two pieces of equip-
via air distribution systems in buildings. Consider-
ment stand out above all others in noise levels and
ations for vibration control are given in chapter 8.
actually dictate the need for unusually heavy
walls or floors, its good engineering to prepare
6-2. Indoor Sound Analysis.
noise-level specifications on those pieces of equip-
a. The approach suggested here is essentially a
ment and require that they be brought under
flow diagram of sound from source to receiver,
reasonable noise limits. If this approach is used
following certain prescribed steps.
successfully, reduced noise can be achieved and
(1) The SPL or PWL values are obtained for
less expensive building designs can be used. It
each noise source (from appendix C or other
would be reasonable, first, to specify sound levels
available source date).
that range about 3 dB below the levels quoted in
(2) The acoustic conditions inside the MER
the manual. Such specifications would not seri-
source room and in the receiving rooms are calcu-
ously limit the availability of equipment, but they
lated.
would weed out the noisiest equipment.
(3) The SPL values of all equipment sources
(2) Use of noise control treatments. This sub-
are extrapolated to the interior MER walls and
ject is discussed in paragraph 6-6. For some types
surfaces of interest (chap 3).
of equipment, a noise control treatment may be
(4) Noise criteria are selected for all the re-
more practical and less expensive than the prob-
ceiving rooms of interest (chap 2).
lems of accommodating the untreated noisy equip-
(5) Wall and floor designs are selected to
ment with strengthened building structures.
permit acceptable amounts of equipment noise into
(3) Building layout alternatives. By recogniz-
the adjoining spaces (chap 4).
ing and applying the material in the manual,
(6) Additional material in paragraph 6-6 is
many noise problems can be reduced during the
considered if special noise control treatments are
design stage. In the building layout, critical spaces
required. The procedures offered here are simple
should be moved away from the mechanical rooms
6-1
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