Abstract:
In order to detect the depth of the low-frequency underwater sound source，an adjustable detection system based on acousto-optic diffraction and the wetting effect was set up. A aluminum cylinder was placed in the surface of natural water. Due to wetting effect the liquid surface was curved, so that the underwater acoustic signal was able to transmit to the water-air interface generating surface acoustic wave(SAW). The amplitude and phase of incident layer beam will be modulated by SAW, and diffraction pattern appears. Thus, acousto-optic diffraction of low frequency underwater acoustic signal was achieved. Diffraction pattern is clear and stable. Changing the depth of the sound source, diffraction patterns are different. Theoretically, by analyzing the relative intensity distribution of the diffraction patterns, the amplitude of surface acoustic wave can be calculated, and the analytic expression of surface wave amplitude was derived. By fitting the relationship between surface wave amplitude and the depth of the sound source, the expression formula was given mathematically. It is can be found that the surface wave amplitude decreases with the increase of sound source.
