ON SOUND ENERGY SCATTERED BY A RIGID-BODY NEAR A COMPLIANT SURFACE

A theorem is derived which generalizes the classical extinction theore m (also known as the optical theorem) to cases where a rigid scatterer of arbitrary shape is located near a large compliant surface which ha s quite general mechanical properties, including dissipation and wave- bearing features, and where the acoustic media on both sides of the co mpliant surface may have different densities and sound speeds. The the orem relates the sound energy scattered from incident planar acoustic waves to the far field pressure in the specular reflection direction a nd that in the transmission direction, determined by the Snell's law. From this simple relation, the scattered energy can be found almost tr ivially from the far field pressures in these two particular direction s; the energy calculation then completely avoids integration of energy flux over control surfaces.