CHAPTER 3
NOISE AND VIBRATION CONTROL
FOR ENGINE INSTALLATIONS
floors, ceilings, and buffer zones to control noise
3-1. Engine noise control.
escape from the engine room to the adjoining or
There are essentially three types of noise problems
other nearby rooms (refer to N&V manual). A
that involve engines and power plant operations:
reciprocating engine should be fitted with a good
Engine noise has the potential of causing hearing
exhaust muffler (preferably inside the engine
damage to people who operate and maintain the en-
room), and if the discharge of the exhaust pipe at
gines and other related equipment; engine noise is
its outdoor location is too loud for building occu-
disturbing to other personnel in the same building
pants or nearby neighbors, a second large-volume,
with the engine (or in a nearby building); and pow-
low-pressure-drop muffler should be installed at
er plant noise is disturbing to residential neighbors
the end of the exhaust pipe. The approval of the
living near the plant. Noise control is directed to-
engine manufacturer should be obtained before in-
ward meeting and solving these three types of
stallation and use of any special muffler or muffler
problems. In addition to the noise control proce-
configuration, because excessive back-pressure can
dures contained n the N&V manual, this manual
be harmful to the engine (para 33 discusses re-
provides material on mufflers, duct lining, vibra-
active mufflers). A turbine engine will require both
tion isolation of engines, the use of hearing protec-
an inlet and a discharge muffler (para 34 discusses
tion devices (ear plugs and ear muffs), and a special
dissipative mufflers), and an engine cover (table
application of room acoustics in which the indoor
27) will be helpful in reducing engine room noise
noise escapes outdoors through a solid wall or an
levels. An air supply to the room must be provided
opening in the wall. Each of the three types of
(for room ventilation and primary air for engine
noise problems requires some of these treatments.
combustion) for both reciprocating and turbine en-
a. Noise control for equipment operators.
gines, and the muffled, ducted exhaust from tur-
Equipment operators should be kept out of the en-
bine engines must be discharged from the building.
gine room most of the time, except when they are
Vibration isolation is essential for both types of en-
required to be in the room for equipment inspec-
gines, but reciprocating engines represent the
tion, maintenance, repair, or replacement. When
vibration problem.
more
serious
Large
personnel are in the room, and while the equipment
reciprocating engines must not be located on upper
is running, ear protection should be worn, because
floors above critical locations without having very
the sound levels are almost certain to be above the
special sound and vibration control treatments. All
DoD 84dB(A) sound level limit. Various forms of
reciprocating engines should be located on grade
engine covers or enclosures for turbine engines are
slabs as far as possible from critical areas of the
usually available from the manufacturers. Data on
building (categories 1 to 3 in table 3-2 of the N&V
the noise reduction provided by these marketed
manual). Vibration isolation recommendations are
covers can be approximated from table 27. A sep-
given in paragraphs 3-6, 3-7, and 38.
arate control room beside the engine room or a
c. Control of noise to neighbors by outdoor
suitable personnel booth located inside the engine
sound paths. If an engine installation is already lo-
room can be used by the operator to maintain visu-
cated outdoors and its noise to the neighbors is not
al contact with the engine room and have ready ac-
more than about 10 to 15 dB above an acceptable
cess to it, yet work in a relatively quiet environ-
level, a barrier wall can possibly provide the neces-
ment. The telephone for the area should be located
sary noise reduction (para 65 of the N&V manu-
inside the control room or personnel booth. An ex-
al). If the existing noise excess is greater than
ample of a control room calculation is included in
about 15 dB or if a new installation is being consid-
paragraph 83b of the N&V manual and in para-
ered, an enclosed engine room should be used. The
graph 42 of this manual.
side walls and roof of the room (including doors and
b. Noise control for other personnel in the same
windows) should have adequate TL (transmission
(or nearby) building with the engine. Noise control
loss; para 54 of the N&V manual), ventilation
for this situation is obtained largely by architectur-
openings for the room and engine should be acous-
al design of the building and mechanical design of
tically treated to prevent excessive noise escape,
the vibration isolation mounting system. The archi-
and, finally, the total of all escaping noise should
tectural decisions involve proper selection of walls,
be estimated and checked against the CNR rating
3-1
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