Abnormal attenuation of powerful ultrasound propagating in cavitating liquids

The remote automatic control system is used to measure the sound pressure in a rectangular container filled with liquids. Research shows that with the increasing of driving sound pressure, sound pressure of near field rises continuously but attenuates faster, whereas sound pressure of far field increases firstly and then abnormally decreases. The change regulation of different frequency components of waves during propagating could be obtained by analyzing the frequency spectra of sound pressure at different positions. Analysis combining with the spectra shows that the abnormal process should be attributed to that the nonlinear oscillation of cavitating bubbles transfers more acoustic energy to harmonics which attenuate faster under higher driving pressure, which results in the pressure of far field being lower than that of lower driving pressure.