A new way for underwater acoustic signal analysis: The morphological filtering

This study presents an innovative way for underwater acoustic signal analysis. It is based on multi-directional filters implementation on time-frequency representation, where each filter is designed to enhance a given direction on the time-frequency plane. To do so, the proposed technique processes the time-frequency plane by taking into account the actual atom and its neighborhood for each direction, up to a given distance. Thus, such an approach emphases information about signal directional features into the time-frequency plane. Derivation of the technique relies first on the use of a recursive algorithm which estimates noise level. Then, after establishing filters responses for one direction, the design method is extended to all-direction, leading to the morphological filtering, which allows specific morphological feature patterns detection from the time-frequency plane. This paper finally presents experimentations on real underwater acoustic recordings to show performances obtained with this technique when objective is SNR enhancement and acoustic signature features preservation.