Determination of Material Properties of the Sea Bed from the Acoustic Plane Wave Reflection Response.

摘要

Investigation of acoustic bottom reflectivity attempt to infer the structure of the sea bed (e.g., the density and sound speed profiles) from a limited knowledge of the reflection coefficient. For many applications, an adequate model to study the acoustic interaction is provided by the scattering of plane waves from a one-dimensional inhomogeneous medium. In contrast to formally exact solutions to this inverse scattering problem, Candel et al. (Journal of Sound and Vibration, vol, 68, 1980, pp. 571-595) propose an approximate scheme that can be readily implemented numerically. Their method applies the forward scattering approximation to a local wave decomposition of the acoustic field. As a result, the plane wave reflection coefficient is obtained as a nonlinear Fourier transform of the logarithmic derivative of the local admittance. Inversion of the integral transform enables the recovery of admittance versus depth by means of a numerical integration using a single impulse response from the sea bed. Separate recovery of both the density and sound speed profiles requires at least two impulse responses corresponding to two distinct grazing angles. This paper appraises an implementation of Candel et al.'s inversion algorithm for the recovery of the density and sound speed profiles from two realistic geoacoustic models of the sea bed for which bandlimited impulse responses were synthetically generated. (Author)