An estimation of absorption coefficients measured in a small reverberation chamber

This paper describes a simple and practical technique for measuring absorption coefficients of a material utilizing a small reverberation chamber. The chamber is used as a sound insulation box as well as a chamber for a reverberant sound field. The chamber does not have an ideal diffuse sound field but a sound field just for absorption measurements. A method based on the sound intensity technique using array microphones has been adopted to measure the absorption coefficients. Many loudspeakers are arranged in the chamber in order to improve the directivity distribution of the incident sound power near the surface of the absorbing material and m simulate a random incident sound field. Theoretical and experimental considerations regarding the effect of multiple sound sources in a small reverberation chamber and regarding the dependence of measured reverberant absorption coefficients on the distribution of sound power directivity are presented.