Study Of Source Velocity Estimation Based On Sound Field Interference Structure

The interference patterns of low frequency broadband ship radiated noise carry the information of target and marine environment,which can be used for passive location of underwater source.Generally,the extraction of interference structure requires horizontal array with large aperture,which brings inconvenience to the engineering implementation.Therefore,the relevant research on how to use the interference structure obtained by single hydrophone has attracted wide attention.Based on the interference features extracted from the received signals of a single hydrophone,this paper studies the algorithm that estimate source motion parameters.The details are as follows:Firstly,according to normal mode theory in shallow water,the types of normal mode are analyzed combined with sound propagation method.Then the characteristics of wideband intensity interference structure and waveguide invariant are discussed.The waveguide invariant distribution in different sound speed gradient profiles is extracted by two-dimensional Fourier transform.Finally,the influence of different normal mode on the waveguide invariant distribution is analyzed.Secondly,due to the complex characteristics of normal mode in ocean environments,an optimization algorithm is proposed for estimating the target motion parameters using twodimensional Fourier transform based on the time-frequency interference structure of the received signal from a single hydrophone in this paper.This method uses two-dimensional window functions in the time-frequency domain to suppress the sidelobes of finite-length Fourier transforms.The dominant mode of interference structure is analyzed combined with marine information,which improves the applicability of the target motion parameters estimation in shallow water.The results of numerical simulation and sea trials show that the optimization method has good performance in negative speed gradient profile and elastic seabed environment,and the estimated results agree with the motion parameters of the source.In addition,an estimation algorithm of source depth and radial velocity is proposed.In this method,the amplitude distribution of the frequency-modal Doppler frequency shift domain extracted by single hydrophone is taken as the matching quantity,and the objective function is constructed according to the least square principle.The motion parameter estimation of the source is realized without prior distance information in the far-field condition.The simulation results show that the proposed method has good applicability under the conditions of different sound speed profiles and different motion parameters of the source.It can still have a good estimation accuracy when the seabed parameters are mismatched,and can estimate the radial velocity of the sound source more accurately under low signal-to-noise ratio condition.The results of simulation and experimental data processing show that the two methods proposed in this paper can estimate the radial velocity of moving targets by acoustic interference characteristics with received signal of single hydrophone,and further realize the estimation of the initial distance and depth of the source,which has a potential application prospect.