A passive range method of underwater source based on single hydrophone

Abstract

Aiming at the passive impulse wideband source range problem in shallow water waveguides, a passive source range method with single hydrophone which is applied to the shallow water waveguide with a bottom of liquid semi-infinite space is presented in this paper by combining the group delay theory and warping transformation. The receive signal is composed of several normal modes, and each mode represents many characteristics of the waveguide environment. Warping transformation is a good tool which can achieve the separation and extraction of normal modes from the received signal, and it is also an unitary and reversible transformation, so the warped signal of each normal mode can be recovered completely. The dispersion curves of normal modes can be extracted by warping transformation, and the relation between arrival time and frequency of each order normal mode can also be calculated, and then the time delay of arriving hydrophone between arbitrary two different normal modes is obtained. According to the group delay theory, different order normal mode has different arrival time at the same frequency, and the arrival time of normal mode is determined at its group speed when the distance between the source and hydrophone is certain. So the propagation range can be estimated when the time delay and the slow group speed difference between two different normal modes are known. When the waveguide environmental parameters are known, the slow group speed difference of arbitrary two normal modes can be calculated by KRAKEN. However, when the bottom parameters are unknown, the bottom reflection phase shift parameter is an important parameter describing the acoustic parameters of the bottom, and it contains nearly all the bottom information, what is more, the bottom reflection phase shift parameter is also a parameter that can be extracted by some experimental data easily. When the depth and the average sound speed of the water column are known, the slow group speed difference between two order normal modes can be represented by the seafloor phase shift parameter. Therefore, the source range can be represented by the bottom reflection phase shift parameter, the sea depth and the mean sound speed in the waveguide, and under this condition, the source location can be estimated by one single hydrophone. The effectiveness and accuracy of the method are proved by the numerical simulation results and sea experimental data processing, in which the signals are both received by a single hydrophone. The sea experimental data contain linear frequency modulation impulse source signal and explosion sound source signal, and the mean relative error of range estimation is less than 10%.