Acoustic and membrane wave interaction at plate junctions

The interaction of an acoustic wave with two joined flat plates results in a diffracted acoustic wave emanating from the junction. The plates are assumed, for simplicity, to have different masses but no stiffness, and the exact solution of the two-dimensional diffraction problem is derived as a Fourier integral. The diffraction coefficient for a plane acoustic wave is found to depend in a simple manner upon the product of the total acoustic pressures at the junction for waves incident from the source and receiver directions. Also, the diffraction coefficient .:lisplays a maximum as a function of frequency, which is interpreted as a quasires. onance phenomenon. The results for the flat, massive plates are extended by perturbation methods. to consider the acoustic interaction with longitudinal (membrane) waves originating from the junction of two curved shells, joined so that their tangent is continuous. Relatively simple results are found for the acoustic-to-membrane coupling coefficients, and these again show strong dependence on frequency. The related problem of membrane-to-acoustic diffraction is analyzed, and the diffraction coefficients obey simple reciprocity relations with the acoustic-to-membrane coefficients.