A simulation model of the pulse returns for a short-range SAS

Numerical simulations of sub-marine acoustical experiments can often save significant sea-time but to have any value, the simulation needs to produce believable results. This paper looks at a simple acoustic simulation which relies on the scattering surface (the seafloor) being approximated by a collection of sub-wavelength smooth rectangular facets. The experiment being modeled is a monostatic, pulse-echo sonar working in extremely shallow water (<;2m in depth). Various modifications to the model of the seafloor are explored to see what assumptions and approximations influence the seafloor reverberation. Volume reverberation from the underlying sediments is not considered. The motivation for this work is to see how feasible it is to operate a broad-beam, broad-band synthetic aperture sonar in extremely shallow waters so a significant part of this investigation is to measure how the phase of the pulse echo evolves as the sonar head tracks over the rough seafloor under extreme reverberation conditions. Our conclusion is that the model is useful for small seafloor areas but not for large surface areas which require too much computation.