Bottom reverberation for large receiving depth in deep water

Abstract

Ocean reverberation is an important issue in underwater acoustics, which usually influences the working performance of the active sonars significantly. The deep-water reverberation data are collected from the South China Sea experiment including the reverberation signals at large receiving depths near the bottom, showing that the wave intensity increases obviously at some moments with time increasing. To analyze in depth the data, a uniform bottom-reverberation model is proposed based on the ray theory, which can calculate monostatic and bistatic reverberation intensity and explain the generation process of deep-water reverberation. The mesh method is first used in this model by dividing bottom scatterers into a number of grids. Then reverberation is calculated based on the exact time of generating the scattering signal from each grid. Due to the exact arrival time, the presented model can provide more accurate result than classical models, in which scatterers are usually treated as circular rings or elliptical rings. Numerical results are compared with experimental reverberations at different receiving distances and depths. The simulated and experimental results agree well overall for large receiving depths, whereas agreement extent decreases for the case of receiving depth close to the sea surface. The analytical results indicate that the applied scattering coefficient is suitable for this experimental sea area, and meanwhile verify that this scattering model is more accurate for low-angle bottom backscatters corresponding to the reverberation at large receiving depths.