THE ACOUSTIC EMISSIONS FROM SINGLE-BUBBLE SONOLUMINESCENCE

Detailed measurements of the acoustic emissions from single-bubble son oluminescence have been made utilizing both a small 200-mu m aperture PVDF needle hydrophone, and a focused 10-MHz transducer. Signals obtai ned with the needle hydrophone show a fast (5.2 ns), probably bandlimi ted rise time and relatively large pulse amplitude (approximate to 1.7 bar). Below the sonoluminescence threshold, the emissions are observa ble, but considerably smaller in amplitude (approximate to 0.4 bar). S everal signals are observed with the 10-MHz transducer and correspond to acoustic emissions from the bubble during the main collapse, as wel l as from the rebounds. Experiments reveal that the acoustic emissions occur at or near the minimum bubble radius. Calculations of the peak pressures and pulse widths are compared with experimental data. (C) 19 98 Acoustical Society of America. [S0001-4966(98)03203-2].