Scattering of an acoustic Gaussian beam from a fluid-solid interface

Abstract

The reflection and refraction of a three-dimensional acoustic beam, whose amplitude is Gaussian in cross section, at a fluid-solid interface is studied. The acoustic Gaussian beam is constructed by assigning complex values to the source coordinates of an acoustic monopole, a technique used in optics to model coherent light beams. The incident beam is specularly reflected except at certain critical angles of incidence of which the Rayleigh angle is the most important. Near this angle the incident beam excites both a leaky Rayleigh wave and a reflected beam, and the interference between these two disturbances produces a shifted and distorted reflected wavefield. The incident beam, near normal incidence, is refracted into a compressional beam and a shear beam, both of whose amplitudes are Gaussian in cross section. Whereas the incident beam has a circularly shaped cross section, both transmitted beams have elliptically shaped cross sections. [Work supported by NSF.]