Sonoluminescence from Bifrequency Excitation of Cavitation Bubbles

The nonlinear response of a single bubble to a bifrequency excitation is much more significant than the linear response. This can have important consequences on the characteristics of acoustic cavitation. The nonlinear response to a bifrequency excitation in comparison to a monofrequency one, consists in the possibility of giving rise to bubble collapse and transient cavitation in an extended range of bubble radii. To test this, a series of experiments has been conducted by a pulsed ultrasonic technique which allows a better characterization of the initial stages of the development of the cavitation zone. Experimental results in water show that the sonoluminescence intensity increases and the threshold for transient cavitation is lowered simply by adding a small percent in power of irradiation with ultrasound of different frequency.