Experimental Approach to the Effect of Diffusers on the Sound Attenuation in Long Enclosures

Abstract

The objective of this paper is to experimentally demonstrate the effect of diffusers on the sound attenuation in long enclosures. For this purpose, a ribbed diffuser and a Schroeder diffuser were tested in a 1:16 scale model of an underground station. It is shown that for both train noise and loudspeaker sources, and under conditions of both high and low absorption, the diffusers are effective for increasing the sound attenuation along the length. With carefully designed diffuser distribution the extra sound attenuation caused by the ribbed diffuser could be more than 6 dB and the effectiveness of the Schroeder diffuser is even greater. It is also demonstrated that the diffusers could be useful for improving the intelligibility of a multiple loudspeaker public address system in long enclosures by increasing the sound energy of the nearest loudspeaker and avoiding the disturbance from the neighbouring loudspeakers. In principle, the measurements are in correspondence with the theoretical analysis.

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