High-Frequency Scattered Envelope Statistics of Patchy Seafloors

The scattering properties of the individual components of seafloors consisting of discrete patches of different materials may have a complicated relationship in terms of their angular response and/or frequency dependence. Consequently, this relationship directly influences the angular and frequency response of scattered envelope probability density functions (pdfs). In this paper, the influence of the relative scattering strength of seafloor patches on scattered envelope statistics will be explored through both a modified form of a recently developed model [Abraham and Lyons, IEEE J. Ocean. Eng., vol. 27, pp. 800-813, 2002] and analysis of experimental data collected off Elba Island, Italy, in May 2003, by the NATO Undersea Research Centre, La Spezia, Italy. Qualitative comparisons of the K-distribution shape parameter (alpha) between that predicted by the model and that measured from data display promising similarities such as the inverse relationship between alpha and bandwidth, the relative difference in values of alpha for the various seafloor types studied, and the dependence on grazing angle. The favorable model/data comparisons show that it is possible to link the scattered envelope distribution to measurable geoacoustic properties, providing the foundation necessary for solving several important problems related to the detection of targets in non-Rayleigh clutter including performance prediction for different systems based on seafloor properties, extrapolation of performance to other system/bandwidths, and optimization of system parameters such as bandwidth to local environment.