Page 260 - Master Handbook of Acoustics

FIGURE 12-14 Absorption coefficients of Sonex contoured foam of various thicknesses for mounting
A.

Drapes as Sound Absorbers

Drapes are a porous type of sound absorber because air can flow through the fabric. This penetration

allows absorption to occur. Variables affecting absorbency include type and weight of material,
degree of fold, and distance from the wall. The heavier the fabric, the greater the sound absorption.
Heavy velour drapes can provide good absorption, whereas lightweight drapes provide practically
2
no absorption. Figure 12-15 compares the absorption of 10, 14, and 18 oz/yd velour hung straight
and presumably at some distance from the wall. The greater absorption in going from 14- to 18-oz/yd 2
2
than in going from 10- to 14-oz/yd is difficult to explain. The effect is concentrated in the 500- to
1,000-Hz region.