Multipath reverberation modeling for shallow water acoustics

Sonar performance can be limited by a number of factors including hardware design, signal processing, and the environment. In environments where the sonar range is much greater than the water depth, multipath interference will frequently be the limiting noise source. To design, or adaptively vary, the vertical apodization of the transmitter and receiver, it is necessary to estimate both the level and angle of arrival of multipath interference. A simple model has been developed to predict the influence of individual multipath rays through second order multipath. The perturbation approximation is used to model the reverberation from both the sea surface and the sea floor. Sea-floor roughness is assumed to have a power law spectrum, with spectral strengths and exponents taken from experimental tests performed in a given environment. Surface roughness is based on a Pierson-Moskowitz spectrum. An example comparing a high frequency and low frequency imaging sonar system will be presented.