利用高频矢量声场和海洋背景噪声的被动地声反演技术

Passive geoacoustic inversion using high frequency vector sensor and ocean ambient noise will be investigated in this project. Utilizing the directivity and the geoacoustic information included in the particle velocities, especially inside the vertical velocity component, we will study the performance of geoacoustic inversion by a small aperture high frequency vector sensor array (VSA), including the seabed parameter sensitivity and the theoretical performance limits of the estimation variance. Using the propagation model of the surface sheet noise travelling downwards, the matched bottom reflection loss (BRL) inversion method will be studied. Furthermore,the high resolution BRL estimation algorithms will be examined. Also based on the ambient noise, the fathometer method using a VSA or single/twin vector sensor will be investigated to estimate the depths of the seabed and the subbottom reflective interfaces. The research in this project is established in theoretical analysis and real data verification,aiming to push forward the vector sensor based passive geoacoustic inversion method. It would provide an effective approach for compact ocean obseverations, and it is promising to be used in autonomous underwater vehicles (AUVs) for rapid ocean explorations and finds applications in surface/subsurface target classifications.

本项目研究基于高频矢量水听器和海洋背景噪声的被动地声反演技术。利用矢量水听器的指向性和振速分量尤其是垂直振速分量中包含的地声信息，研究小孔径高频矢量阵地声反演的性能，包括海底参数反演的灵敏度和估计方差的理论性能限。利用海面薄层噪声自上而下的传播模型，研究其海底反射损失匹配反演的性能，并研究高分辨海底反射损失估计方法。同样基于海洋背景噪声，研究矢量阵或单/双矢量水听器的被动回音测深技术，对海底和各地层反射界面的深度进行估计。本项目的研究立足理论和试验数据验证，推动高频矢量水听器被动反演的发展，为水下便携式海洋参数观测提供一种有效途径，在水下自主航行器的快速海洋勘测以及水面/水下目标分辨方面将有应用前景。

围绕基于海洋背景噪声场的地声反演和被动回音测深技术，分别用不同声场模型对矢量阵地声参数反演的性能限展开了分析，结果表明声压和振速联合处理的性能最佳，并提出了两步遗传算法用于反演海底声速，反演性能得到很大提高，首先用遗传算法反演压缩波速，接收距离和深度；随后用优化后的距离和深度作为反馈提高仿真声场的精度，再次反演压缩波速给出了更高的精度和更准确的结果。实现了基于噪声场互谱密度矩阵Toeplitz性拓展基阵孔径以提高反射系数提取精度的方法，仿真表明该方法可达到两倍基阵孔径的反射系数提取精度。提出了用敏感核分析参数扰动对噪声场相干性影响的方法。实现了基于噪声场垂直振速信号的多途结构提取方法研究，该方法可快速提取垂直分置两点间的物理多途到达结构，有效抑制虚拟头波等非物理到达途径。相较于声压信号，用垂直振速信号可以缩短多途结构提取所需的噪声信号长度。本课题研究成果为分布式探测与警戒系统等需要快速提取主要海底参数提供了一种解决途径。