Effect of Hydrophone Tip Shape on Acoustic Field and Acoustic Cavitation Behavior

We have developed a tough hydrophone that was damage-resisted in a high-intensity field. The influence of the tough hydrophone's shape on the spatial distribution of acoustic bubbles in the 22 kHz field was investigated using visualization of acoustic bubbles by using high-speed video camera. Two hydrophones of different shapes with a flat-shape tip and a conical-shape tip were located around an anti-node and a node of sound pressure. In the case of flat-shape tip located at pressure antinode, acoustic bubble clouds were generated on the tip, an amplitude of output signal was changed though the applied voltage to the transducer was same. In contrast, there was no bubble sticking on the conical-shape tip even though the bubbles were readily generated around this region. Furthermore, a similar tendency of less sticking bubble on the conical-shape tip was observed when the tip was located around pressure node that the bubbles were not readily generated. In the case of conical-shape tip, the bubble clouds at the hydrophone tip were significantly reduced because of its shape, although the generation of acoustic bubbles in the high-intensity ultrasound fields cannot be avoided.