Research On Bottom Reverberation Modeling And Its Correlation Property In Shallow Water

Bottom reverberation of the shallow sea has always been a hot issue in the study of underwater acoustics.Previous research was usually based on the empirical scattering model which is detrimental to the study of its physical mechanisms and more complex bistatic three-dimensional problems.Therefore,according to the generation of bottom reverberation,acoustic scattering on different types of seabed(fluid,elastic,poro-elastic)was studied firstly,including the surface scattering of interface roughness and the scattering due to volume inhomogeneity in sediments.For acoustic scattering of the rough interface,the differences between two classical methods(perturbation and Kirchhoff approximation methods)and small slope approximation were analyzed.The results show that using the method of small slope approximation to deal with the roughness scattering has higher accuracy and wider applicability than the classical theory.At the same time,the properties of roughness scattering on different media were analyzed with the method of small slope approximation.For volume scattering,the perturbation scattering theories of fluid and elastic media were included.The scattering characteristics of different media were analyzed and the effect of acoustic scattering on sound propagation was briefly discussed by the theories.Then the above physical scattering models were combined with the ray model and the normal mode model which were used to build the ray and the normal mode reverberation models.Due to the advantages of normal mode theory in dealing with the field in shallow sea,the characteristics of bottom reverberation were analyzed by the normal mode reverberation model.Firstly,the intensities of monostatic and bistatic reverberations were calculated with the model,and the relationship between the strength of monostatic and bistatic reverberations was analyzed.Secondly,we analyzed the variation of reverberation intensity caused by roughness scattering and volume scattering with respect to different geoacoustic parameters.Thirdly,the vertical correlation of the monostatic reverberation was calculated.Its properties,variation rules and influence mechanism were presented.Finally,the model was used to predict the reverberation in time domain,and the statistics of the bottom reverberation were obtained.