利用海洋环境噪声估计浅海海底表层声速

为提高反演效率,提出一种快速估计浅海海底表层声速的方法。根据噪声能流理论,垂直阵接收的海洋环境噪声数据能够用于无源提取海底反射损失,反射损失曲线中具有明显的临界角效应,从而接估计海底表层声速。以射线模型为基础,推导了噪声提取的反射损失与理论值之间的差异,并讨论实际阵列波束形成在不同角度和频率下的性能。考虑到非等声速环境下声线会发生弯曲,需对角度进行修正以提高方法的广泛适用性。不同频率的临界角与有效深度之间存在对应关系,黄海某海区数据处理结果表明,在临界角不变的有效深度内,海底表层可以视为等声速层,该海区海底表层0.5 m内声速估计结果为1547 m/s,与有源反演结果相近。 

Estimating the sound speed of the surface layer of the seabed using ocean ambient noise in shallow water

In order to improve the inversion efficiency,a method for quickly and directly estimating the sound speed of the surface layer of the seabed is proposed.According to the energy flux theory,the ocean ambient noise data received by the vertical line array can be used to passively extract the bottom loss.Obviously,the bottom loss curve has an effect of critical angle,which is used to estimate the sound speed of the surface layer of the seabed.Based on the ray model,the difference between the bottom loss of noise extraction and the theoretical value is derived,while the beamforming performance of the array at different angles and frequencies is discussed.Considering that the sound ray will bend under the environment of non-constant sound gradient,the angle needs to be corrected to improve the universality of the method.There is a corresponding relationship between the critical angles of different frequencies and the effective depth.Data processing result of the Yellow Sea shows that within the effective depth where the critical angle remains unchanged,the surface layer of the seabed can be regarded as a constant speed layer.The sound speed of the surface layer of the seabed in this sea area is estimated at 1547 m/s within 0.5 m,which is similar to the active inversion result.