Cavitation threshold dependence on the rate of the transducer voltage variation

The cavitation thresholds of subharmonic emission and of sonoluminescence in water have been measured in a focused ultrasound beam by two different methods: (1) by increasing the transducer voltage at different rates; (2) by keeping a chosen constant transducer voltage and waiting for the appearance of the subharmonic or of the sonoluminescence. The thresholds increase with increasing the rate of voltage increase. The waiting time diminishes with the increase of the chosen threshold voltage.