为了对低频液体表面波的衰减系数进行测量，利用液体表面波的光衍射方法，得到了稳定、清晰的衍射图样，并发现了衍射条纹强度分布与光斑入射点位置有关。对此进行了理论分析，得到了衍射条纹强度分布与液体表面波振幅之间的解析关系式以及表面波振幅随距离变化的实验数据。结果表明，可以根据衍射条纹的强度分布来测量液体表面波的衰减系数，与经典流体力学理论相比较，符合较好。这一结果对测量液体的物理参量是有帮助的。

In order to measure the damping constant of the liquid surface acoustic waves at low-frequency,steady and visible diffraction patterns were obtained by means of diffraction method and it was found that the variation of intensity distribution was related with the position of light spot. After analyzing the relationship between the intensity distribution of the diffraction rings and the liquid surface wave amplitude,the damping constant was obtained. The experimental data are in good agreement with classic hydrodynamics theory,which proves that the diffraction method is applicable for measurement of liquid parameters.