Acoustic propagation analysis near the first Central Atlantic convergence area

Deals with spatio-temporal analysis of propagation rays received on an array before, within and after the first convergence area in Central Atlantic. The modelisation of this situation shows that the temporal distribution of the energetic arrivals is rapidly variable versus propagation distance and depth. In order to characterize accurately this phenomenon, a specific experimentation has been organized off the Azores by the French Navy, whose received data are very interesting for those conditions of propagation. After propagation, the transmitted signal is received on an array of fixed hydrophones and also upon a vertically moving hydrophone. Identification of the several paths is thus possible. Thanks to high resolution spatio-temporal methods such as Wide-Band Active Music, it is possible to define precisely the spatio-temporal response of the medium inside this area of propagation characterized by the presence of caustics. In the first part of the paper, the authors describe the experimentation and the method. Then, experimental results are compared with predictions given either by ray-tracing modelisation and normal modes analysis