The effect of fluid–structural coupling on sound waves in an enclosure—Theoretical part

Abstract

This paper presents a theoretical investigation into the effect of the interaction between a sound field and its boundaries upon the characteristics of the sound field in an enclosure. Recent experimental measurements have shown that the boundaries of the sound field in a reverberation room cannot be correctly described in terms of a locally reactive normal acoustical impedance. Fluid–structural coupling must be taken into account if the mechanism of sound decay in the reverberation room is to be understood. A solution based on modal coupling analysis is obtained for the decay of sound waves in a panel–cavity system. The vibration of the system is resolved into a number of acoustical modes (including fluid and structural vibrations). The reverberation times and the resonance frequencies of different modes are calculated as a function of the modal parameters of the uncoupled panel and cavity. The effect of the panel characteristics on the decay behavior of the cavity sound field is investigated. The interesting phenomena of maximum sound absorption and resonance frequency ‘‘jump’’ are identified and interpreted in terms of the coupling behavior of the panel and cavity modes.