会聚区的水平偏移特性及其临界频率分析

利用数值模型研究了完整深海声道中会聚区的水平偏移特性,根据折射定律和Lloyd镜效应推导了会聚区发生水平偏移时临界频率的表达式。研究结果表明:当声波频率低于临界频率时,会聚区的主导模态与频率相关,随着声波频率减小会聚区会向靠近声源的方向水平移动,同时传播损失明显增大,当声波频率大于临界频率时,会聚区的主导模态近似与频率无关,会聚区的位置和传播损失大小不会随频率改变而发生明显变化,声源深度不同时,临界频率也不同。通过临界频率可以确定在特定声源深度下,会聚区发生水平偏移时需要满足的频率条件,利用临界频率与声源深度之间的关系,可以被动估计深海浅层目标的深度。

Analysis of horizontal migration characteristics of convergence zone and its critical frequency

The horizontal migration characteristics of convergence zone in complete sound fixing and ranging channel is studied by simulation model.The critical frequency of this phenomenon is derived according to Snell's law and Lloyd's mirror effect.It is found that when sound frequency is lower than critical frequency,the dominant mode of the convergence zone is frequency dependent.With the decrease of frequency,the convergence zone moves horizontally towards sound source,and the transmission loss increases significantly.When sound frequency is higher than the critical frequency,the dominant mode of convergence zone is almost frequency independent and the position and transmission loss of convergence zone will not change significantly with frequency.Most notably,the critical frequency varies with source depth.Critical frequency can be used to determine the frequency condition that need to be satisfied when convergence zone horizontally migrates at a specific source depth.The critical frequency formula contains source depth information which provides a good avenue for shallow target depth estimation in deep ocean.