Geoacoustical parameters estimation with impulsive and boat-noise sources

Localization is a crucial issue in underwater acoustics: when an underwater source is detected, the next step consists of localizing it. To do this, environmental parameters must be known or estimated. How can we estimate these parameters? As underwater sources produce low frequency (<100 Hz), most of the seismic processing tools developed by petroleum research can be adapted to estimate geophysical parameters of the sea and the seafloor. To know which methods or representations are useful to estimate geoacoustical parameters, a study of the propagation between an underwater source and receivers laid on the floor is proposed in the case of a real waveguide. Then, geoacoustical parameters are estimated on real data using transformations such as velocity correction or frequency-wavenumber transform. To validate these methods, two wavepropagation simulations using a finite-difference algorithm are made: the first in an environment similar to the model used to estimate geoacoustical parameters and the second in a more realistic environment (with several layers of sediments and variable water layer depth). Geoacoustical parameters are estimated and compared to the values used in the simulation. Finally, impulsive source is replaced by a boat-noise source to show that it is still possible to estimate geoacoustical parameters using noise sources.