参量阵辐射的声波在水-沙界面的传播

T.G.Muir等人指出参量阵辐射的声波在水-沙界面的透射同常规平面波透射相比较,具有两个特点:第一,透射波的峰值出现在联接水中发射换能器和沙中水听器的直视角方向上,而不是出现在Snell折射定律所规定的方向上;第二,当入射角大于临界角时,透射波掠角不为零,而且其衰减比较小。
在理论分析和实验研究的基础上,本文指出,这些异常现象是由参量阵的体积阵特性、沙层介质的吸收特性以及特定的实验方法所致。文中描述的等阵长参量阵入射情况下的研究结果,证实了上述论点,指出声参量阵辐射的声波在分层介质中的传播本质上依然满足Snell折射定律。参量阵的视线传播现象在某些应用中具有实际价值。

PROPAGATION OF THE DIFFERENCE-FREQUENCY WAVE GENERATED BY A TRUNCATED PARAMETRIC ARRAY THROUGH WATER-SEDIMENT INTERFACE

T. G. Muir et al. observed experimentally that the maximum of the received sound pressure in the sediment insonified by a parametric array departed significantly from the prediction of Snell's law. The wave fronts penetrated more steeply into the sediment and the attenuation with depth was less than that predicted by plane wave theory at the postcritical incidence.
It was found that due to the variation of the length of parametric array and the variation of the attenuation in the sediment, the maximum of the received sound pressure occurs at the line-of-sight between projector and hydrophone. It has been proved both theoretically and experimentally that Snell's law is still valid when the length of parametric array and the attenuation in the sediment are kept constant. Due to the contribution of the secondary sound close to the boundary, the postcritical penetration of a parmetric array can be deeper. The lateral wave should be considered at the postcritical incidence .