On the classification of underwater acoustic signals. I. An environmentally adaptive approach

Abstract

Environmental conditions and geometries have a pronounced effect upon the signals received as scattered underwater acoustic waveforms. The use of these environmental factors is important. However, these factors are often ignored or at best are introduced indirectly in the formulation of composite hypothesis testing when analyzing the received signals and classifying causes of the scattering. Here we develop a methodology which permits one to introduce estimates of the current environmental state (i.e., certain environments and geometries) in order to adapt the classification algorithm to the situation. The pertinent features of statistical-physical models of the medium (as proposed by Middleton, for example) are useful guides to the experiments needed for the definition of these environmental states. The implications of an environmentally adaptive approach are discussed, and procedures for estimation, feature extraction, and feature selection are presented. [Work supported by the Naval Sea Systems Command.]