Page 245 - The Master Handbook Of Acoustics

220 CHAPTER NINE

ED C B A
10

7
8"
5

6"
3
4"
2 2"
Perforation, percent 1 1"

0.7

0.5

0.3
Panel
thickness 3 /16"
0.2

0.1
50 100 200 500 1,000 2,000
Frequency, Hz
FIGURE 9-34
A graphic presentation of Eq. 9-4 relating percent perforation of perforated panels, the
depth of air space, and the frequency of resonance. The graphs are for a panel of 16″
3
thickness. (See also Fig. 9-21.) (A) For 1″ furring lumber. The lines are drawn to corre-
3
spond to furring lumber which is furnished, e.g., the line for 8″ is actually 7 4 air-
space. (B) For 2″ furring lumber. (C) For 4″ furring lumber. (D) For 6″ furring lumber.
(E) For 8″ furring lumber.