Identification of seabed geoacoustic parameters from transmission loss data

This report deals with the identification of seabed geoacoustic parameters by means of wave propagation experiments in ocean acoustics. The objective function, which measure the difference between the computed and observed transmission loss of the sound field in the water, is minimized with respect to unknown bottom parameters. We have tried several optimization algorithms and wave propagation models and studied their performance for the solution of the inverse problem. In addition, we have developed computational tools to quantify the influence of seabed parameters on the sound field in the ocean. This analysis shows that long-range sound propagation in the sea is mainly affected by three bottom parameters: the velocity, its gradient and the attenuation of the upper layer of the seabed. These parameters can be determined by a fast matched-field inversion provided that the water depth is constant and the sound velocity profile of the water is known. Our results also show that uncertainties about the sound velocity of the water and range-dependent sea environments make the inversion much more difficult.