Effects of target-boundary acoustic coupling in shallow water scattering

A null field T-matrix formalism is developed for scattering a pressure wave from a stationary elastic shell immersed in a homogeneous and isotropic fluid half space and in proximity to a fluid-elastic interface with periodic roughness. It is shown that the shell-interface T-matrix is simply related to the free field T-matrices for the shell and the rough interface and that the formalism contains multiple scattering on the rough surface as well as between the rough surface and the shell. Some of the low order Floquet spectral amplitudes for scattering from the shell-interface system are calculated and used to show some of the effects of the acoustic coupling between the shell and the rough surface.