Difference Factor of Vertical Beam Pattern for Shallow-Water Source Depth Discrimination

This study addresses the problem of source depth discrimination in the context of shallow-water acoustics. From the perspective of beam pattern correlations, a discriminating characteristic quantity, which implies the information of source depth, is presented and defined as the difference factor of the vertical beam pattern. In applying the proposed difference factor for source depth discrimination, the corresponding discrimination method and judgment criterion are presented. Numerical results, obtained by processing SwellEx-96 data recorded by a vertical line array (VLA), indicate the potential of the proposed method in source depth discrimination. This method also shows the correct discrimination of VLA signals with different frequencies by using the plus/minus sign of the difference factors of the vertical beam pattern. Effects of array aperture, array depth, signal-to-noise ratio (SNR), and environment mismatch on the performance of the current method are also analyzed to indicate the robustness of the method. Finally, the SwellEx-96 data results indicate that the proposed method is insensitive to the initial range and radial speed from the VLA to the source target.