Effective Absorption of Sound Absorbing Materials for Acoustic Design of Studios

ABSTRACT

Effective absorption coefficient of absorbing materials has been measured at various frequencies from 125 to 4000 c/s. under different mounting conditions in chambers of different volumes. It has been found that in the frequency range where Sabine's coefficient for the material is maximum, the value of effective absorption coefficient is greater than the Sabine's coefficient. It varies appreciably with the mounting conditions. When the material is divided in patches and mounted on all the surfaces of the chamber, the smaller the patches the higher is the maximum value. The effect of total area of the material used and the volume of the room, on the effective values of absorption coefficient, is comparatively small. It has been shown that if values measured in diffused sound field under proper mounting conditions are used, the acoustic treatment of a studio can be planned fairly accurately. Also by judicious selection and installation of the material the cost of the acoustic treatment of a studio can be reduced and not more than about 30 per cent of the total surface need be covered with acoustic materials to obtain the optimum R/T values suggested by Morris and Nixon.