| In a waveguide environment,the acoustic signal is heavily influenced by the properties of the seabed.Seabed geoacoustic parameters play a crucial role in various underwater acoustic applications,and the seabed scattering coefficient is a critical parameter that describes how sound waves scatter due to features of the seabed.Therefore,determining seabed acoustic parameters and scattering coefficients is highly significant.Ocean acoustic inversion methods are often used to retrieve ocean environmental parameters.Three natural phenomena,noise,reverberation and propagation,are usually used in ocean acoustic inversion.In order to reduce the influence of inter-parameter correlations on the inversion results,other data can be added to carry out joint inversion.This thesis focuses on the joint inversion of geoacoustic and scattering parameters based on reverberation data and channel model.The paper analyzes the inter-parameter correlations and their impact during reverberation inversion.Due to the lack of sufficient information in the input data for inversion and the interparameter correlations,multiple solutions occur,making it necessary to perform joint inversion based on reverberation data and channel model of propagation.To improve the accuracy and reliability of joint inversion,the paper performs joint inversion of single and multi-frequency data.Firstly,joint inversion of single-frequency data is carried out,and through parameter sensitivity and correlation analysis,the necessity of joint inversion of multifrequency data is indicated.A modified method,called the multi-frequency multi-step joint inversion method,is proposed by analyzing the results of commonly used multi-frequency joint inversion methods.The multi-step joint inversion method employs a sensitivity-based parameter inversion approach,where the parameters are inverted in a descending order of their sensitivity.This method reduces the impact of inter-parameter correlations on the inversion results and ensures the reliability of the inversion outcomes for less sensitive parameters.Additionally,this multi-step strategy reduces the number of forward model calls required for computation,thereby shortening the inversion time.Based on the validation of simulated data,the paper carries out data processing and analysis of sea trial data.To analyze the impact of seafloor sediment changes on received reverberation intensity,a reverberation data-channel model of propagation joint inversion method is used.Firstly,seabed geoacoustic parameters are inverted based on ship noise,and the inversion result is then applied to a seabed reverberation model for inversion of scattering coefficients based on the reverberation data,the results of which are-31 dB and-26 dB.The validity of the proposed method is verified by simulation and sea trial data processing.The inversion results of measured data are in good agreement with the exploration results in the test area,which shows the feasibility of using long-range sonar system to retrieve the seafloor. |
