TM 5-805-4/AFJMAN 32-1090
Table 5-7. Approximate Noise Reduction of Typical Exterior Wall Constructions.
Octave
Wall Type
Band
C
F
A
B
D
E
G
(Hz)
10
22
28
8
12
17
31
0
14
63
9
24
32
0
13
19
25
34
20
10
14
20
0
125
26
27
36
11
15
22
250
0
28
500
12
30
38
0
24
16
1000
13
17
0
26
29
33
42
2000
0
14
18
28
30
38
48
4000
15
31
19
0
30
43
53
33
8000
16
0
20
30
48
58
No wall; outside conditions.
A:
B:
Any exterior wall construction, with open windows covering
about 5% of exterior wall area.
c:
Any typical wall construction, with small open air vents
of about 1% of exterior wall area; all windows closed.
D:
Any typical wall construction, with closed but operable
windows covering about 10-20% of exterior wall area.
E:
Sealed glass wall construction, 1/4 in. glass thickness over
approximately 50% of exterior wall area.
Approximately 20 lb/ft.2 solid wall construction with no
F:
windows and no cracks or openings.
Approximately 50 lb/ft.2 solid wall construction with no
G:
windows and no cracks or openings.
the residence would have been a few dB higher
would tend to average out the cooling tower
if the louvered surface of the cooling tower faced
directivity characteristics. Typically source direc-
the residence or a few dB lower f the end surface
tivity is difficult to obtain. Source directivity for
of the cooling tower faced the residence. In
certain sources is included under appendix C. If
Location B, the orientation of the cooling tower
source directivity information is unavailable as-
would have been less critical, because the bar-
sume that the sound source radiates uniformly
rier and other reflecting surfaces on the roof
in all directions.
5-13
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