匹配垂直质点振速的浅海地声参数反演

海底声学参数对海洋波导中的声场特性研究和相关应用具有重要意义。针对一次夏季黄海声传播实验,分析了浅海负跃层环境下垂直质点振速的传播特性和简正波结构,说明当声源和接收器均位于负跃层下时,除海底附近外的大部分深度上垂直质点振速能量较高,且与声压相比,号数高的简正波对垂直质点振速的贡献更大,利用垂直质点振速进行匹配场反演能获得更高的海底参数敏感性。分析了海底吸收系数对垂直质点振速匹配场反演的影响,结果表明只有当进行匹配场反演时设置的海底吸收系数接近真实值时,才能获得准确的海底声速、密度和海深反演结果。利用实验中矢量水听器获取的垂直质点振速信号进行匹配场反演,将海底吸收系数在变化范围内取不同值对海底声速、密度和平均海深进行全局搜索,根据代价函数值最大确定了海底声速、密度及平均海深的反演结果,并利用不同距离上的声压传播损失反演出不同频率下的海底吸收系数。根据反演得到的海底声学参数计算声压传播损失,与实验中声压水听器测量结果符合较好。

Geoacoustic inversion in shallow water by matching vertical particle velocity

Bottom acoustic parameters are significant for the research of sound propagation properties and corresponding applications in ocean waveguides. The propagation properties and the normal-mode structure of vertical particle velocity in the ocean environment with a thermocline in shallow water are studied for the experiment conducted in the Yellow Sea in summer. It is shown that vertical particle velocity has higher energy at most depth except for near-bottom depth when the source and the receiver are both under the thermocline. Moreover, high-order modes contribute more to vertical particle velocity and vertical-particle-velocity-based Matched-Field-Processing (MFP) inversion method can acquire higher sensitivity to bottom parameters in comparison with sound pressure. The influences of the bottom absorption coefficient on the vertical-particle-velocity-based MFP inversion method are studied, it is shown that the accurate sound speed, density and water depth can be obtained only when the bottom absorption coefficient is set around the real value during the MFP procedure. By using the vertical particle velocity signals acquired by the vector hydrophones during the experiment and searching the sound speed, density and water depth under different bottom absorption coefficient, the stable inversion results are acquired. The transmission losses of the sound pressure at different ranges are used to invert the bottom absorption coefficient. The transmission losses of sound pressure calculated by using the inverted bottom parameters are in consistent with the measured results acquired by the pressure hydrophones in the experiment.