Passive Localization Based on Multipath Time-Delay Difference with Two Hydrophones in Deep Ocean

In this study, we propose a localization method based on multipath time-delay difference (MTD). We extract the time-delay difference of the direct and sea surface-reflected sound rays by the signal from hydrophones in deep sea to establish the MTD matching vector. The predicted matching vectors are obtained using Bellhop to build an ocean acoustic field model. The spatial distribution of MTD are simulated and analyzed. The matching ambiguity plane is obtained by the objective function. The maximum point of ambiguity plane is the position of the sound source. We show that the sound field propagation error can be replaced by the geometric error. We then analyze the influence of the received position error on the localization accuracy. The effects of errors caused by skewing of hydrophone and horizontal variation in SSP are studied. Simulation and experimental results at sea show that the proposed method is robust and can locate the sound source with a small aperture array of two hydrophones.