Effects of sound radiation on Sabine absorption coefficient of modally-reactive panels

Abstract

A modally-reactive panel in a room absorbs and radiates sound at the same time when it is excited acoustically by the enclosed sound field. The absorption of sound occurs when only part of the incident sound is reflected by the panel, but when the entire panel vibrates, the radiation of sound is also produced. In this paper, Statistical Energy Analysis (SEA) is used to establish a relationship between the acoustic-structural coupling of the panel with the sound field and the Sabine absorption coefficient of the panel. It is shown that the coefficient does not only consist of the sound absorption by the panel from the room but also, the sound radiation from the vibrating panel back into the room. Computational and experimental examples are presented for different acoustical properties of the panel and the sound field to illustrate the extent of influence of the sound radiation on the coefficient. The results provide a basic understanding of the conditions in both cases where the sound radiation has significant effects and negligible effects on the determination of the Sabine absorption coefficient of modally-reactive panels in rooms.