A new unified theory for scattering of a bounded acoustic beam from a liquid-solid interface near the Rayleigh angle

摘要

For scattering of a bounded acoustic beam from a liquid-solidinterface,the principal difficulty comes from the treatment of the plane wave reflec-tion coefficient.In the Present paper,following the Singularity Expansion Method,the reflection coefficient is expanded into the sum of an analytic function(constant1)and the principal part of the Laurent expansion in the neighborhood of theRayleigh pole.The scattered field is now evaluated by a double integral in thewavenumber and interface planes.The constant 1 produces a rigid boundary geo-metrical reflected beam,and the expansions at the Rayleigh poles yield the leakyRayleigh waves.It is particularly proved that the residues of the poles are nearlyproportional to the imaginary parts of the poles for most liquid-solid interfaces.Therefore,the complex pole may determine the whole behavior of the leakyRayleigh wave,including the excitation and reradiation efficiencies.For thebackscattered field,since the negative Rayleigh pole plays a major role,a back-ward