While the generation of cavitation leads to many interesting and exploitable phenomena, it is necessary to accept that under normal circumstances the pressures required to do this are of the order of 100kPa amplitude at 20 kHz in water.
This represents a threshold requirement and minimum energy expenditure. However, bubbles driven by much lower driving field (of 10’s pa amplitude) will also be able to do useful work. In this case a tuned approach is necessary where the acoustic conditions match or are close to the resonant frequency of the bubble in question. At this point an energy saving of several orders of magnitude is possible with only a small loss in effect. In our group we have been examining bubble oscillation using low amplitude sound fields. The figure below shows surface waves generated in this way and their effect on local mass transfer rates.