Broadband Models for Predicting Bistatic Bottom, Surface, and Volume Scattering Strengths

Abstract : Multistatic active system performance can be driven by reverberation from the ocean boundaries and biologics. Providing accurate sonar performance predictions of reverberation, in turn, relies on providing accurate estimates of bistatic scattering strengths. This report presents new three-dimensional models that provide physics-based estimates of the dependence of scattering strength on the incident and scattered grazing angles, the bistatic angle, the acoustic frequency (10 to 10000 Hz), and physical descriptors of the environment (such as bottom properties for the bottom model, wind speed for the surface model, and fish properties for the volume model). The bottom model describes scattering from rough, elastic interfaces while the surface model describes scattering from both the rough air-sea interface and subsurface bubbles. The volume models describe scattering from dispersed bladdered fish, including boundary-interference effects. For all, parameter studies along with data-model comparisons demonstrate the importance of using physics-based scattering models to describe the complex acoustic interaction processes at the active performance/reverberation models (such as the Comprehensive Acoustic System Simulation (CASS) or the Bistatic Range-dependent Active System Performance (BiRASP) models) and inverse algorithms (such as environmentally adaptive techniques).