Origin of the broad-band noise in acoustic cavitation

The broad-band noise has been experimentally used to monitor the cavitation activity in a sonochemical reactor, an ultrasonic cleaning bath, a biological tissue, etc. However, the origin of the broad-band noise is still under debate. In the present review, two models for the mechanism of the broad-band noise are discussed. One is acoustic emissions from chaotically (non-periodically) pulsating bubbles. The other is acoustic emissions from bubbles with temporal fluctuation in the number of bubbles. It is suggested that the latter mechanism is sometimes dominant. Further studies are required on the role for bubble cluster dynamics as well as the bubble-bubble interaction in the broad-band noise especially at relatively low ultrasonic frequencies.

Automated summary

Broad-band noise is used to monitor cavitation activity in various applications, but its origin is still debated. This review discusses two models for the mechanism of broad-band noise: acoustic emissions from chaotically pulsating bubbles and acoustic emissions from bubbles with temporal fluctuation in number. The latter mechanism may be dominant and further studies are needed on bubble cluster dynamics and bubble-bubble interaction in the broad-band noise, especially at low ultrasonic frequencies.