Ways to Reduce Re
fl
ections and Interference
To reduce re
fl
ections and interference:
Increase the distance of travel for the re
fl
ections by changing the angle of incidence. If the
angle of incidence is near a corner but not focused directly at a corner, the re
fl
ections will
bounce off both walls and scatter throughout your chamber rather than bounce off one wall
before converging at the center of the chamber.
Increase the damping factor by covering hard surfaces (metal, tile, wood, plastic, etc.) with
soft, spongy, non-re
fl
ective, sound absorbing materials (carpet, foam, etc.).
Figure 4 - A sound chamber used for testing and calibrating speakers
The walls and table top in Figure 4 are covered by 1 inch foam pads with 1 inch tall pyramid
projections (total thickness of 2 inches) for increased scattering.
c (m/s)
f (Hz)
λ
(mm)
∆
(mm)
-
-
c/f
λ
/4
343.2
4000
85.8
21.45
343.2
8000
42.9
10.725
343.2
16000
21.45
5.3625
343.2
32000
10.725
2.68125
1.
2.
Sound Chamber Fundamentals | 52
