Source depth estimation using modal decomposition and frequency-wavenumber transform

Source localization in shallow water environment is a crucial issue in underwater acoustics. Many methods based on Matched Field Processing (MFP) or on modal decomposition (also called mode filtering) have been developed using a vertical array. The conventional mode filter separates modes using a vertical array of hydrophones. In this case, modes amplitudes are estimated by spatial integration of the pressure field which becomes impossible with a horizontal array. In this paper, we propose an efficient method to estimate the source depth by modal decomposition of the pressure field recorded on a horizontal array of hydrophones. Modes amplitudes are estimated using the frequency-wavenumber transform, which is the 2D Fourier transform in time and radial distance. Then predicted modes amplitudes are compared to measured modes amplitudes, and source depth is estimated. Robustness against noise of the method is studied and application on real data is presented.