Monostatic and bistatic scattering from a density contrast surface

Abstract

Chu’s formalism for the impulse response of a point source to a density contrast isovelocity wedge [J. Acoust. Soc. Am. 86, 1883–1896 (1989)] is of significant practical importance, since it facilitates the extension of wedge diffraction boundary scattering models to rough penetrable surfaces. The method is used here to study scattering from an experimental surface described by Li et al. [J. Acoust. Soc. Am. 96, 3715–3720 (1994)]. The geometry contains both interior and exterior wedges, and allows the diffracted scattering component to be studied independently of the reflected component. For density contrast values which emulate rigid boundary conditions, the formalism correctly models the experimental results, and duplicates predictions of the Biot–Tolstoy solution for a rigid wedge [J. Acoust. Soc. Am. 29, 381–391 (1957)]. The formalism is then used to investigate an assumption commonly made in boundary scattering work, i.e., that scattering levels can be effectively estimated by scaling the predictions of a rigid surface scattering model by the reflectivity of the surface. The results suggest that the assymption is most valid for monostatic (backscattering) configurations, and less good for bistatic cases, with increasing differences occurring between interior and exterior wedge geometries. [Work supported by ONR.]