Origin of broadband acoustic emission from a dancing cavitation bubble

Abstract Acoustic cavitation generates bubbles exhibiting violent expansion and contraction under intense ultrasound in liquids. The acoustic emissions (AE) spectrum from cavitation bubbles contains harmonics, subharmonics, ultraharmonics, and broadband noise, depending on the bubble dynamics. Broadband noise is used to characterize the extent of acoustic cavitation although its origin is under debate. This study presents synchronous measurements of AE spectrogram and high-speed images of a dancing bubble in a single-bubble sonoluminescence system. A time-resolved correspondence between the results by the two techniques revealed that fragmentation and coalescence are the origin of broadband noise.