利用深海海底反射声场特征的水面声源被动测距

Passive ranging of surface source using bottom bounced sound in deep water

海底反射声工作方式是指声波经一次海底反射到达接收器的工作方式,是深海影区内水声探测的重要途径.依据射线声学理论,深海海底反射声工作方式下的声场由海底反射路径(BR)、海面-海底反射路径(SBR)、海底-海面反射路径(BSR)、海面-海底-海面反射路径(SBSR)起主要贡献,4条路径声波的到达时间不同,利用其到达时延差可以分析深海海底反射声工作方式下的声场强度干涉结构.分析发现,海底反射声区声场强度在频率域呈现周期性,且频率间隔随距离增加而增大,且频域间隔对应于多途时延差的倒数,因此可以利用多途时延差与距离的关系来估计声源距离.对于水面声源,声源处的海面反射可以忽略,因此其海底反射声场由BR和BSR传播路径的声波起主要贡献,其干涉条纹的频域间隔对应于BR路径和BSR路径时延差的倒数.本文通过分析深海海底反射声工作方式下声场强度干涉结构,得到了多途时延差随距离变化的关系,并将其应用于水面声源的被动测距,仿真结果和实验结果均证明了该方法的有效性.

Bottom bounced pattern in deep water interprets the pattem under which rays arrive at the receiver through the paths hitting the bottom boundary once, and it is of great importance in underwater acoustic detection in shadow zone. Based on the ray theory, the bottom bounced sound field in deep water is mostly contributed by four eigenrays including bottom-reflected （BR） path, surface-bottom-reflected （SBR） path, bottom-surface-reflected （BSR） path and surface-bottom-surface-reflected （SBSR） path, all of which arrive at different time with different time delay. On the basis of the time delay of four eigenrays, the interference striation pattern of the bottom bounced sound field can be derived. From the derivation, it can be found that the striation appears periodic in the frequency domain at a certain source-receiver range, and the period increases with range increasing. As the frequency period corresponds to the reciprocal of multipath time delay, the range can be estimated by the time delay. As for a near-surface target source, surface reflection at the source could always be neglected, and then the sound field can be thought of as the contribution of BR path and BSR path. As a result, the frequency period of its striation corresponds to the reciprocal of the time delay between BR path and BSR path. In this paper, the relationship between the time delay and range is obtained by analyzing the interference striation pattern of the bottom bounced sound field in deep water, and then it is applied to passive ranging of surface sources. The approach is demonstrated valid by the simulated data. Experimental results shows that the range of the surface source can be estimated effectively, with an estimation error less than 5%.