James F. Ball
Natl. Ctr. for Phys. Acoust., Univ. of Mississippi, University, MS 38677
The pressure in the scattered sound field of an elastic structure in water can be represented in the standard form of the Kirchhoff--Helmholtz integral with the free-space Green's function [see, for example, A. D. Pierce, Acoustics: An Introduction to its Physical Principles and Applications (ASA, New York, 1989), p. 182]. This integral, over the surface of the elastic scatterer, involves terms in both the normal component of displacement and the acoustical pressure at the surface. These quantities are of course not independent of each other, the surface pressure being derived from the surface displacement by means of an integral equation. It is of interest, however, to examine the relative contribution of the pressure terms and the displacement terms to the backscattered sound in the far field. This is computed for an aluminum solid sphere and spherical shell.