Research On Layered Seabed Reverberation Based On Parabolic Equation Method

Seafloor reverberation has always been a hot issue in underwater acoustics research and one of the important interference factors for active sonar target detection.The study of the intensity and signal characteristics of seafloor reverberation is of great significance for active sonar performance prediction and seafloor environment inversion.Shallow water reverberation is an important field of marine acoustics research.Previous studies on reverberation were mainly based on ray models and empirical scattering models,neglecting the influence of the layered structure of the seabed on sound propagation and scattering.While these approximations can be used for high-frequency signal simulations,the impact of the seabed’s layered structure cannot be ignored for the propagation and scattering processes of lowfrequency sound waves in shallow water environments.Moreover,the significant undulations of the seabed in shallow water environments require a more rigorous approach for studying shallow water reverberation.This paper presents the establishment of a layered seabed scattering model based on the acoustic-seabed interaction model.By considering the scattering directions for monostatic and bistatic sonar systems,two-dimensional and three-dimensional seabed scattering models incorporating seabed parameters and interface roughness are developed.Through this model,the relationship between the scattering intensity of the layered seabed and parameters such as grazing angle,frequency,different layered structures,and seabed types is analyzed,providing insights into the regularities and characteristics of layered seabed scattering.Employing the parabolic equation theory,a sound propagation model in the marine environment is established,enabling analysis of the impact of layered seabed structures and irregular undulations on shallow water sound propagation.Building upon this,the layered seabed scattering model is combined to create a simulation model for shallow water seabed reverberation.The model is validated through simulated calculations of reverberation signals and intensities for monostatic and bistatic sonar systems,further supported by experimental data.Utilizing the developed seabed reverberation model,statistical characteristics and relative decay laws of reverberation signals in layered seabed environments are analyzed through simulation calculations.Considering that the actual seafloor topography has large scale random undulations,the simulation model of seafloor reverberation in randomly undulating topography is further established,and the influence of topography on seafloor reverberation is analyzed to summarize the characteristics of marine reverberation.