浅海波导中目标回声计算的射线声学方法

建立一种基于虚源法和物理声学方法计算浅海波导中目标回声的射线声学方法。入射声线经过两个界面的多次反射有无限多条,每条入射声线由目标反射后又会产生无限多条到达接收点的声线。将各种组合的散射声场求和得到总的回波声场。用射线声学方法计算了Pekeris波导中半径10 m的绝对软球的回声随距离的变化。与已有文献中波动声学方法的计算结果对比,两者在平均值和下降趋势上符合。计算表明,波导中球和一些圆形目标的等效目标强度(ETS)与自由空间中目标强度(TS)差别很小。而像圆锥形这类目标的等效目标强度与自由空间中目标强度差别较大,导致传统的声呐方程误差较大。与波动声学方法相比,射线声学方法不但具有明确的物理意义,而且可以对浅海信道中复杂形状目标回声进行计算。 

The geometrical acoustic method for calculating the echo of targets submerged in a shallow water waveguide

A geometrical acoustic method based on image-source method and physical acoustic method is developed to calculate the target echo in the shallow water waveguide. The incident rays are reflected by two boundaries for many times, and then the back rays become countless. The total back scattering field is obtained through summing up the scattering field produced by each combination of incident rays and back rays. The echo of the 10 m-radius pressure release sphere in Pekeris waveguide with the range is calculated by the geometrical acoustic method. Compared with the results calculated by the wave acoustic method in the obtained literature, it shows that both are in accordance on average value and descend trend. The following results indicate that the difference between Equivalent Target Strength (ETS) in shallow water and the Target Strength (TS) in free space for spheres and certain other rounded objects is small. However, the ETS of some targets such as cone-shaped is quite different from TS in free space, which can lead to large errors in estimating a target's scattering property using traditional sonar equation. Compared with the method of wave acoustics, the geometrical acoustic method not only has the definite physical meaning but also can calculate the echo of complex objects in shallow water waveguide.