TM 5-805-4/AFJMAN 32-1090
Table 7-5. End Reflection Loss.
A. Terminated at Acoustic Tile Ceiling or in Free Space.
Octave-Band Center Frequency (Hz)
Circular Duct
Mean Duct Width
63
125
250
(Inches)
500
1K
6
14
9
20
5
2
8
12
7
18
3
1
10
10
6
16
1
2
9
12
5
14
2
1
7
16
3
12
0
1
6
20
10
2
0
1
5
9
2
24
0
1
4
8
1
28
0
0
7
3
32
1
0
0
3
6
36
1
0
0
48
2
5
1
0
0
72
1
3
0
0
0
B. Terminated Flush with Hard Ceiling, Wall, or Floor.
Circular Duct
Octave Band Center Frequency (Hz)
Mean Duct Width
63
125
250
500
1K
(inches)
6
18
13
8
4
1
8
10
16
6
2
1
10
9
14
3
2
1
8
12
4
13
0
1
16
6
10
2
0
1
20
9
5
2
0
1
4
24
8
1
0
0
28
7
3
1
0
0
32
6
2
1
0
0
36
5
2
1
0
0
4
48
1
0
0
0
1
72
2
0
0
0
7-8
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