基于简正波模态的浅海声传播的最佳深度规律研究

Optimum depth of shallow water acoustic based on normal modes

在给定距离情况下,声能量在深度方向上的分布并不均匀,体现在声传播损失在不同深度之间的差异可达20dB,因此研究深度方向上的声传播损失最小点即最佳深度对水声通信和探测有一定帮助。采用简正波方法对最佳深度的影响因素进行研究,得出声源频率、声源深度和海水深度对最佳深度的影响最大,并在理想液体波导中研究了海水深度和声源频率主导的简正波模态阶数对最佳深度影响,得出在给定声源深度情况下,简正波阶数是影响最佳深度的唯一因素。当海水中简正波阶数从1逐渐增大时,最佳深度也从海水层中部逐渐向海面和海底移动,当简正波个数足够多时,最佳深度稳定在声源深度和声源的对称深度。

At a given distance,the distribution of acoustic energy in the depth direction is not uniform,which is reflected by the difference of transmission loss of different receiver depths which could rise up to 20 dB,so it is helpful for underwater acoustic communication and detection to locate the optimum depth.The influence factors of the optimum depth are studied by the normal modes methods.It is found that the source frequency,source depth and water depth have great influence on the optimum depth.The influence that the number of normal modes have on the optimum depth has been studied in the ideal waveguide.The conclusion is that the number of modes are the root cause of the optimal depth.When the number of normal modes in seawater increase from one,the optimal depth also moves from the middle of the sea layer to the sea surface and the sea floor.When the number of normal waves is sufficient,the optimal depth is stabilized at the depth of the sound source and its conjugate depth.