Geoacoustic Parameter Inversion Based On Sound Field Propagation Characteristics In The Shallow Water

The most important environmental parameters for underwater acoustic propagation calculation are composed of Marine water environmental parameters and submarine acoustic parameters,which are more difficult to be directly measured than water environmental parameters.Therefore,the study on the effective acquisition of these parameters has always been a hot topic in underwater acoustic science.The acoustic inversion method can replace the direct measurement of a large range of sea areas,and can obtain the sediment parameters of the whole test sea area quickly and cheaply,which has a good development prospect.Aiming at the problem of obtaining sound parameters of shallow sea bottom,this paper proposes an inversion method of 5 sound parameters of shallow sea bottom,which is based on bayesian theory,including p-wave sound velocity,s-wave sound velocity,p-wave attenuation,s-wave attenuation and density.In the process,firstly,the theoretical prediction value of the sound pressure field is calculated by the fast field method(FFM).According to the Bayesian theory,we establish the misfit function between the measured sound pressure field and the theoretical pressure field.Finally,posteriori probability density(PPD)of the parameters is given as the inversion results according to the Metropolis criterion.Then the uncertainty of the inversion results is analyzed from a statistical point of view.In order to verify the feasibility and reliability of this method,numerical simulation and laboratory tank experiment data are respectively adopted to carry out inversion research in this paper.The research results show that:(1)Compared with the traditional inversion method,this method uses the posteriori probability and statistical characteristics of the comprehensive information of the inversion parameter vector to represent the inversion results when the traditional inversion method that can only provide the estimation of parameters to be inversion,the inversion information is more comprehensive and scientific.(2)Under the inversion objective function given in this paper based on bayesian theory,the PPD of the parameter to be inversion can be accurately obtained by using the sampling of Metropolis criterion.(3)S-wave velocities,P-wave velocities and seafloor density have fewer uncertainties and are more sensitive to complex sound pressure than S-wave attenuation and P-wave attenuation.(4)The transmission loss calculated by inversion result are basically consistent with the simulation and experimental results.The prediction result of time domain waveform matches well with the received signal.Without considering the influence of the residual vibration emitted by the transducer,the correlation coefficient of those two reach 0.89,which proves the reliability of the inversion method in practical application.