Underwater transient signal processing: Marine mammal identification, localization, and source signal deconvolution

Processing marine-mammal signals for species classification and monitoring of endangered marine mammals are problems that have recently attracted attention in the scientific literature. For classification it has been proposed to use methods appropriate for non-stationary signals, such as time-frequency and time-scale analysis. This paper shows that a factor that can significantly affect results from marine-mammal signal processing is the impulse response of the ocean in which the signals propagate. The ocean is a dispersive propagation medium and, therefore, affects the time-frequency characteristics of a propagating acoustic signal. Because of this distortion, feature selection should be performed after the oceanic impulse response has been deconvolved from the recorded signals. The paper also discusses localization of vocalizing marine mammals using matched-field processing and shows how this becomes a part of the deconvolution process.