Optical measurement of the liquid surface wave amplitude with different intensities of underwater acoustic signal

A simple measurement system is developed to study the optical effect of the low-frequency liquid surface wave excited underwater acoustic source. The high stability and clear diffraction patterns were observed experimentally. The relationship between the diffraction patterns divergence angle and the distance of the acoustic signal was derived. Furthermore, with the increase in distance, the diffraction patterns divergence angle will decrease. The damping characters of the liquid surface wave were theoretically obtained when underwater acoustic wave spread to the liquid surface. The analytical expression between the diffraction patterns divergence angle and the liquid surface wave amplitude was theoretically derived. It was found that the surface wave amplitude is exponently attenuated with the change of the horizontal distance. The attenuation coefficients are dependent on the frequency of the liquid surface acoustic wave, and the greater the frequency, the smaller is the attenuation coefficient.