Cavitation Empiric Evidence

I have a 40Khz ultrasound generator board and a 40Khz probe.Cause the US genrator has sweeping and sweeping rate settings, is there an empirical way to undestand IF and WHEN cavitation occurs?
I already tryed with and alluminium foil in the water and the foil has been holed, is this cavitation or is only the cleaning power of the US? what does affect the sweep and sweep rate?