拖曳声源深海脉冲多途效应及直达波传播特征

The Multipath Effect and Direct Wave Characteristics of Pulse Waveforms From Towed Sound Source in Deep Sea

深海脉冲传播多途效应显著,直达波受海洋环境影响较大。基于南海某海域深水试验数据,采用Butterworth带通滤波器识别目标信号,进而分析近、中、远距离处VLA接收到的信号特征,并根据射线理论解释多途效应、直达波特征规律。结果表明:近距离目标信号可分为直达波及两次海底反射波;中距离可分为直达波与三次海底反射波;远距离目标信号弱,反射波特征不明显。其中,直达波声强显著低于第一次海底反射波,受夏季海面波导的影响,近表层深度处的直达波强度最大;50~200m深度层在强跃层控制下,声线向下弯曲,直达波信号随深度增加逐渐减弱;随传播距离增加,直达波逐渐减弱消失。

The multipath effect is obvious when sound wave transmits in deep sea environment, and the direct wave is seriously affected by the underwater environment. In this paper, the acoustic data of deep sea investigation in South China Sea is used,and the target signal is gotten using Butterworth band pass filter.Then, the characteristics of the target signal with the small, middle,and large distance received by the V L A are analyzed, and the regular of multipath effect and direct wave is explained based on acoustic ray theory. The results show that the target signal with the small distance can be classified into direct wave and two times of seafloor reflection wave, which is classified into direct wave and three times of seafloor reflection wave with the middle distance,and the target signal with the large distance is not obvious enough to be discriminated.The sound intensity of the direct wave is smaller to the first seafloor reflection wave.Sound intensity is the biggest at the subsurface layer of the direct wave due to surface ducts in summer, and it becomes weaker downward at the depth of 50~200m as the acoustic rays bends down with the control of strong thermocline.Furthermore, direct wave becomes weaker and even unable to discriminate with range increasing.