Matched cross-spectrum phase processing for source depth estimation in deep water

Zhou et al. (2022) proposed a method for instantaneous source depth estimation in deep water using matched beam intensity processing (MBIP) that leverages depth-related oscillatory features arising from Lloyd's mirror interference in the frequency domain (Appl. Acoust., 2022, 186, 108493). However, the efficacy of MBIP diminishes with a random source spectrum. To counteract the effect of a random source spectrum, a vertical line array (VLA) positioned near the sea bottom is employed and a cross-spectrum is generated from the conventional beamforming output, which is achieved by dividing the VLA into upper-half and lower-half arrays. The authors find that the cross-spectrum phase interference pattern is determined by the source depth and is unaffected by the source spectrum. Consequently, a matched cross-spectrum phase processing method is proposed, which demonstrates appreciable depth estimation accuracy compared to that of the existing techniques, as evidenced by the results from both simulated and experimental data.