水与流体饱和孔隙介质界面上非镜面反射声场的实验研究

用光学法和发射-接收法研究了水与流体饱和孔隙介质界面上声波的非镜面反射声场．测量了入射角θ_i为16°－80°范围内的反射系数R，记录了θ_i在Rayleigh波临界角θ_c附近±4°范围内两束反射波的反射角、波束位移△、波形和频谱．实验发现：(1)在θ_c附近±4°范围内，观察到θ_i两束反射波A和B，其中波束B沿界面有波束位移△，实验测出△随θ_i增大而减小，并非在θ_i=θ_c时最大．(2)反射角等于θ_i的波束的频谱很接近于入射波的频谱，反射角等于θ_c的波束的频谱相对于入射波有频谱的负偏移．(3)波束A的相位与发射换能器直达波的相位一致，波束B的相位与波束A相反

EXPERIMENTAL STUDY OF NON-SPECULAR REFLECTED ACOUSTIC FIELD ON A WATER-FSPM INTERFACE

In this paper,the non-specular acoustic reflected field on aWater-FSPM (fluidsaturated porous media interface by the optical method and the transmitter-receiver method.The reflection coefficient R was measured for incident angle of 16°～80°. The reflection an-gles of two beams, their beam displacements, wave forms and spectra were recorded in therange of the incident angle ± 4° near the Rayleigh critical angle θc. The experiment wasfound (1) that for the range θi of ± 4° near θi two reflected beams A and B were observed.The measured displacement △ of the beam B decreases as the incident angle θi increases andis not a maximum at θc = θi, (2) that spectrum of the beam with the reflection angle equalto θi is much closed to that of the incident beam, and the spectrum of the other beam withthe reflected angle equal to θc has a negative shift to that of the incident beam, (3) that thephase of beam A is the same as that of directly received from transmitter, and the phase ofthe beam B is inverse to that of beam A