Study On The Propagation Of Acoustic Wave In Bubble-Liquid Medium

If an acoustic wave propagates in medium, there will be some attenuation of wave due to absorption and dispersion of sound. The absorption of sound is due to viscosity of medium, thermal conduction and relaxation, which make the energy of sound to heat and internal energy of medium. The dispersion is due to the inhomogeneity of medium, which will lead the energy of sound to deviate from its direction of propagation. In order to predict the weather of the sea for a long distance, the strong scattering and attenuation of sound in bubbly liquid have been researched and used to real-time monitoring. As a strong scatterer, bubble has been used to ultrasonic imaging of biological tissue in domain of biomedicine. With more and more interest in Doppler ultrasonic imaging, in use of the second harmonic, of blood stream being provoked, the research of acoustic characteristics in bubbly water is becoming hot again. Recently, some researchers pay attention to the acoustic properties of a bubble-liquid mixture of high viscosity to investigate seismoacoustic phenomena in volcanoes.In detail, the content includes several aspects:1. Based on the theory that viscosity plays the main role in absorption of sound, the sound speed, coefficient of attenuation and valid elastic coefficient in viscous medium are discussed. And the curves of sound speed and coefficient of attenuation following the change of frequency are charted. It is shown that, if the viscosity of medium is low, the sound speed is constant, but the coefficient of attenuation will increase with the increasing of frequency.2. By boundary conditions of pressure and radial vibration velocity in bubble wall, the formula of sound speed and coefficient of attenuation are presented; then, the curves of sound speed and coefficient of attenuation following the changes of bubble volume fraction or frequency are charted. The conclusions are shown: given the same frequency, the sound speed decreases and the coefficient of attenuation will keep on rising with increasing of the bubble volume fraction; given the same bubble volume fraction, there is almost no influence induced by frequency to sound speed, and the coefficient of attenuation still keeps on rising following the increasing of frequency; the radius of...