Coherent versus diffuse surface and volume Reverberation in an ocean wave guide: Reverberation rings, modal decoupling, and possible fish scattering in Geoclutter 2001

Abstract

Conditions necessary for the field scattered from volume inhomogeneities and surface roughness in a wave guide to become diffuse in nonforward azimuths are derived from Green’s theorem. Diffuse scattering leads to a decorrelation of the wave guide modes that simplifies the expression for the intensity of the total scattered field. When diffuse scattering conditions are not satisfied, seafloor scattering becomes coherent and leads to the formation of ‘‘reverberation rings’’ sometimes observed in high-resolution sonar systems. The formation of these rings will be investigated both analytically and with simulations. The possibility that some prominent clutter events in the Geoclutter 2001 experiment are due to diffuse scattering from fish schools is investigated theoretically and experimentally.