Source Depth Discrimination Based on Interference Spectrum in Deep Water with an Incomplete Channel

Abstract

A method to distinguish the surface source and underwater source based on two-dimensional Fourier transform of interference pattern in deep-water environment with an incomplete sound channel is presented in this paper. Considering the modal characteristics of incomplete channel, the normal mode can be divided into three categories: trapped mode, bottom interacting mode and surface interacting-bottom interacting mode. Then, the interference spectrum can be obtained by performing a two-dimensional Fourier transform on the interference pattern. Due to the correlation between the interference structure and the source depth, the types and positions of interference spectral peaks vary at different source depths. Based on this, subspaces can be defined for the interference spectrum, and then the energy ratio of the different modal interference groups in the subspaces can be calculated for source depth discrimination. In this method, the identification of source depth is regarded as a binary classification problem, where the decision threshold is calculated from simulation results under a given false alarm probability. The source depth discrimination can be achieved through comparing the energy ratio with the given decision threshold. The effectiveness of the proposed method is verified using numerical simulations and experimental data.