864 Chapter 29
Table 29.5 : Frequency 1/4 Wavelength Dimension
Hz m ft
30 2.86 11.38
40 2.14 7.04
50 1.72 5.64
60 1.43 4.69
70 1.23 4.03
80 1.07 3.52
90 0.96 3.13
100 0.86 2.82
120 0.72 2.35(^063)
0.1
0.2
0.3
0.4
Absorption coefficient
0.5
0.6
0.7
0.8
0.9
1.0
125 250
Frequency (Hz)
500 1000
Fres (^55) SVHz
Simple cavity
With absorbent in cavity
Volume
V(m^3 )
Length
(m)
Area
S(m^2 )
Figure 29.12 : Typical absorption characteristics of a resonant absorber.