有限阻抗表面扁平目标对声波的散射

Acoustic Scattering from Flat Object with Finite Impedance Coating

本文应用几何衍射理论研究水中扁平小样品的声散射特性．根据有阻抗覆盖层的刚性尖劈衍射的一致性ＧＴＤ公式和几何关系导出矩形扁平样品的散射公式．通过数值计算，讨论了收发合量和收发分置时样品的散射特性，及其与入射波参数和材料性质之间的关系．将计算结果与实验数据进行了对比，其吻合程度较好．ＧＴＤ的数值方法可望应用于目标强度预报和自由场小样品反射系数的测量．

This paper studies acoustie scattering from small rectangular plates by GTD.Samples are made of thin steel, covered with an absorbent material. Scattering expressions are derived using uniform GTD for wedges covered with an impedance layer.Numerical calculations are then carried out;and scattering characteristics of samples in monostatic and bistatic modes discussed.The results show that edge diffraction is closely associated with parameters such as frequency, angle of incidence,sample dimension, material reflectivity, etc. Measurements are taken for a steel plate.The results are in general agreement with numerical computations.It is expected that the GTD based numerical method will eventually lead to some empirical formulae useful in prediction of target strength and free-field measurements of reflectivity of acoustic absorbent materials.