A joint acceptance function for enclosed spaces

Abstract A method is proposed for quantifying the geometric coupling between the acoustic modes of an enclosure and the vibratory motion of the enclosing surfaces. A dimensionless quantity, called the joint acceptance function, is defined which gives the coupling efficiency of an enclosing surface within a range from zero to unity. The joint acceptance function is based on an integral solution to the wave equation which requires a knowledge of the Green function for an enclosed space. Section 2 of the paper is devoted to methods of generating Green functions for enclosed spaces as series expansions in terms of orthogonal eigenfunctions. Computer generated Green functions are shown to compare favorably with those obtained from experiments performed on a hard walled, rectangular box. Section 3 of the paper describes the method of calculating the joint acceptance function for arbitrarily shaped enclosures. Two applications of this function are presented: (a) a rectangular enclosure with surfaces vibrating as simply supported plates, and (b) a practical case involving the reduction of noise in a tractor cabin.