The cavitation threshold 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 transducer voltage and waiting for the appearance of subharmonic or sonoluminescence. The thresholds increase with increasing the rate of voltage increase. The waiting time diminishes with the increase of the chosen threshold voltage.
