New trends for shallow water acoustic tomography
Résumé
Due to multi-path propagation, the estimation and identification of ray arrivals is usually non-trivial on the recorded signals, due to interferences between different paths or to weak Signal to Noise Ratio. Consequently, a kind of solutions has been proposed: the High Resolution estimation methods, based on a modeling of the wavefront; and the wave separation techniques, using transducer arrays. This work is about the second ones. In classical case, where an array of sensors is used, beamforming is performed to separate the ray arrivals by their different propagation angles. In more recent underwater experiments, a double array of emitters and an array of receivers were used. Signal processing tool for this experimental configuration will be presented: It consist on performing double beamforming simultaneously on emitter array and on receive array, and it allows a better separation of waves and a better identification with theoretical raypath. These advantages will be illustrated on real data from the experiment FAF03 and we will present also a tomography results on real data to illustrate the benefit of the double beamforming