Cavitation detection with subharmonic emissions by low intensity sustaining ultrasound

Control of acoustic cavitation by ultrasound pulse wave has been investigated recently. Cavitation detection is an important factor for the cavitation control. In this study, subharmonic detection which has been used to detect the acoustic cavitation in continuous sonication is applied to pulsed ultrasound sequence using low intensity sustaining ultrasound. The sustaining ultrasound follows just after the high intensity ultrasound pulse. The power of the sustaining ultrasound is low enough to avoid cavitation inception by itself. When the cavitating microbubbles are generated and grow to the certain size by the high intensity pulsed ultrasound, the sustaining ultrasound prevents the dissolution due to rectified diffusion. Finally, the bubbles can grow enough to emit subharmonic acoustic pressure. With this method, the cavitation generated by the pulsed ultrasound was clearly detected.