Dolphin localization and motion estimation with a single hydrophone multipath propagation
Résumé
This communication aims at presenting an algorithm that estimates location and speed vector of a dolphin emitting a whistle. This algorithm requires a single hydrophone and applies when direct, bottom-reflected and surface-reflected paths are available. It is well known that multipath echoes make it possible to locate a source with a single hydrophone. This applies to both clicks and whistles. For moving sources, whistles instantaneous frequency laws are scaled by Doppler effect which is a contraction for approaching sources or an expansion for receding sources. The different propagation times and Doppler effects for the different paths are exploited to estimate source location and speed vector. First, we propose to explain how Doppler affects differently the echoes of an emitted whistle. Then we demonstrate how differential Doppler effects existing between bottom-reflected (resp. surface-reflected) and direct paths are used to estimate source speed. Finally, we propose an algorithm that extracts the differential Doppler effect based on the use of time-frequency tools such as high-order ambiguity functions, warping operators and wide-band ambiguity functions. Our algorithm is successfully applied and validated on simulated data, tank measurements and real whistles of common dolphins recorded in Bay of Biscay, France.