西太平洋远距离声传播特性

Characteristics of long-range sound propagation in western Pacific

声信号在海水中能够传播上千千米,远距离声传播与近距离声传播的特性不同.本文利用西太平洋声源与接收最远距离近2000 km的水声实验数据,对实验海区的海洋环境信息、实验使用的接收垂直阵信息进行处理,分析大洋完全声道环境下,远距离声传播能量衰减规律和多途到达结构特性.在远距离传播能量衰减规律方面,随着传播距离增大,海水吸收对声能衰减的作用凸显,海水吸收系数的选取对声场能量预报的准确性至关重要.较低频信号海水吸收较小,中心频率100 Hz的声信号,传播距离从1000—2000 km,传播损失仅增大6 dB左右.深海声道远距离声传播多途到达结构特性方面,实验海区温跃层声速较高,使得到达接收点的本征声线数目更多,多途到达结构更复杂,海面反射声线形成的到达结构处在整体到达结构的靠前位置,且能量相对较强;受西北太平洋副热带模态水的影响,声速剖面存在双跃层结构,导致部分声线到达接收点的时间较早,多途到达结构在时间轴上的长度延长.

Acoustic signals can travel thousands of kilometers in seawater,and the characteristics of long-range sound propagation are different from short range propagation.This paper is based on a long-range underwater acoustic experimental data obtained from the western Pacific Ocean,where the farthest propagation distance is nearly2000 km.The ocean environment information and vertical line array information are carefully processed.We analyze the attenuation of long-distance acoustic propagation in seawater and multi-path arrival structure characteristics under the complete acoustic channel environment of the ocean.In terms of the attenuation law of long-distance propagation energy,with the increase of propagation distance,the effect of seawater absorption on the attenuation of sound energy becomes prominent,and the selection of absorption coefficient is very important for the accurate prediction of sound field energy.Absorption in seawater of low frequency signals is small,and the transmission loss of acoustic signal with 100 Hz center frequency increases only by about 6 dB when the propagation distance increases from 1000 km to 2000 km.In terms of multi-path arrival structure characteristics of deep-sea acoustic channel for long-distance sound propagation,the thermocline sound velocity profile in the experimental sea area has a higher sound speed,making the number of eigenrays reaching the receiving point more and the multi-path arrival structure more complex.The arrival structure formed by sea surface reflected eigenrays is at the earlier position of the overall arrival structure and has relatively strong energy.Owing to the influence of subtropical water over the northwest Pacific Ocean on the sound speed profile,the time of some eigenrays arriving at the receiving point is earlier,and the length of multi-way arrival structure on the time axis is prolonged.