深海大接收深度海底混响研究

Bottom reverberation for large receiving depth in deep water

海洋混响对主动声纳工作性能的影响不可忽略,一直是水声学研究中的一个重要课题.在南海实验中获取了深海混响实验数据,包含近海底大接收深度的混响信号,其强度随时间变化存在锯齿形结构.为对混响数据进行深入分析,基于射线理论提出了一种深海海底混响模型,能够计算本地混响和异地混响强度,并可解释深海混响信号的产生过程.该模型首先对海底散射体进行网格式划分,然后根据每个网格内散射体产生混响信号的准确时间进行混响计算,对于传播路径丰富的深海环境比传统按圆环或椭圆环处理散射体的方式更加精确.在多种收发距离和接收深度条件下,将数值模拟结果与实验数据进行比较.结果表明:对于大接收深度,混响整体吻合较好;而靠近海面处的混响,二者的一致性下降.分析结果表明,使用的海底散射系数参数适用于该实验海区,同时验证了该散射系数模型对于小掠射角海底散射更加准确,对应深海大接收深度混响.

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.