TM S-805-4/AFJMAN 32-1090
Table C-3. Sound Pressure Levels (in dB at 3-ft. Distance) for Packaged Chillers With Centrifgal Compressors.
Sound Pressure Level, dB
Octave
Cooling
Cooling
Band
Capacity Under
Capacity 500
Tons or More
500 Tons
(Hz)
31
92
92
63
93
93
125
94
94
250
95
95
500
91
93
1000
91
98
2000
91
98
4000
87
93
8000
80
87
A-weighted,
97
103
dB(A)
Table C-4. Sound Pressure Levels (in dB at 3-ft. Distance) for
each component making up the assembly. Compres-
Absorption Machines.
sor noise levels should be taken from the packaged
chiller data. Sound level data for the drive units
(motors, gears, steam turbines) should be taken
Octave
Sound Pressure
from the appropriate tables in the manual or
Level, dB
obtained from the manufacturers. Decibel addition
Band
should be used to determine each octave band sum
All Sizes
(Hz)
from the octave band levels of the various compo-
nents. The acoustic center should be assumed to be
31
80
at the approximate geometric center of the assem-
63
82
bly, and distances should be extrapolated from that
point. For very close distances (such as 2 to 3 feet)
125
82
to each component, assume the total sound levels
250
82
apply all around the equipment at distances of 3
feet from the approximate geometric centers of each
500
82
component, although this assumption will not pro-
1000
81
vide exact close-in sound levels.
2000
78
C-7. Absorption Machines.
4000
75
These units are normally masked by other noise in
a mechanical equipment room. The machine usu-
8000
70
ally includes one or two small pumps; steam flow
noise or steam valve noise may also be present.
86
A-weighted,
The 3 foot distance SPLs for most absorption
dB(A)
machines used in refrigeration systems for build-
ings are given in table C-4.
concern, the distance should always be taken from
C-8. Boilers.
the front surface of the boiler. Noise levels are
much lower off the side and rear of the typical
a. Noise data. The estimated noise levels given
boiler. The wise variety of blower assemblies, air
in table C-5 are believed applicable for all boilers,
and fuel inlet arrangements, burners, and combus-
although some units will exceed these values and,
tion chambers provides such variability in the
certainly, many units will be much lower than
noise data that it is impossible simply to correlate
these values. These 3 foot noise levels apply to the
noise with heating capacity.
front of the boiler, so when other distances are of
C-4
Previous Page
