Effect of fluidal—stractural coupling on sound waves in an enclosure in low‐frequency range

Abstract

The acoustic properties of individual normal modes in a rectangular panel‐cavity system were investigated experimentally. The system consisted a heavy five‐sided concrete box closed on the sixth side with a test panel. Experimental evidence in this paper reveals the dependence of the modal decay time of sound waves in the enclosure upon the modal characteristics of the test panel, such as the modal coupling factors, resonance frequencies, and modal decay times of the test panel. The results of experimental measurements are used to verify some of the previous theoretical predictions. The agreement between the measured and calculated acoustical modal decay time shows that the modal coupling theory can be used to evaluate the sound wave behavior in those enclosures, in which the coupling between fluid borne and structure borne acoustical waves is modal and where the classical model based on the locally reactive boundary assumption does not apply. The phenomenon of the maximum sound energy absorption by the panel was also observed in the experiment.