Statistical evaluation of 80 kHz shallow-water seafloor reverberation

Abstract

Knowledge of the background reverberation environment is a prerequisite for the design of any target detection scheme. While the problem of understanding and predicting high-frequency background reverberation level or mean energy scattered per unit area of the sea bed has received considerable attention, studies of high frequency reverberation amplitude statistics are relatively scarce. Of these studies, many have dealt with scattering from more or less homogeneous seafloors in terms of bottom type whereas most shallow water areas will not be homogeneous but will have patchiness in space and time which will have a strong influence on reverberation amplitude statistics. In this work a comparison is presented between 8kHz reverberation statistics obtained at shallow water sites around Sardinia and Sicily. The data include measurements from several distinct bottom provinces, including sites with Posidonia Oceanica sea grass and sites covered with live shellfish. Results of the analysis are cast both in terms of mean power level or backscattering coefficient as well as of the amplitude statistics. The reverberation statistics did not always exhibit a Rayleigh probability distribution function (PDF), but exhibited statistical distributions with heavier tails. Several more appropriate models of reverberation PDF were examined in order to better describe the measured amplitude distributions. The Rayleigh mixture and the K models were found to be the most robust in describing the observed data.