Abstract:
A high-frequency model of bistatic sound scattering is considered assuming an elastic seabed with spatially fluctuating bulk parameters and a slightly rough surface. The first-order perturbation solution is used to obtain an approximate expression for the bistatic scattering strength, different geometric configurations are considered, and the dependence of bistatic scattering strength upon the incident and scattered grazing angles, as well as the ``bistatic,'' or azimuthal angle, is computed for various seabed types. The parameters of the model include mean values for bulk properties and parameters defining the spectra of fluctuations in bulk properties and seabed relief. The influence of shear elasticity is examined by comparison with the case of a fluid seabed having the same density and compressional wave speed. It is shown that shear effects on both roughness and volume components of scattering are small for sands which consequently can be treated as acoustic fluids for realistic shear velocities (approximately 300 m/s and less). For consolidated sediments and rock, shear effects are dominant, complicated, and very sensitive to bottom parameters. Volume scattering exhibits a strong dependence on correlations between the parameter fluctuations as well as their spectral aspect ratio. [Work supported by ONR.]