The cavitation zone generated by a pulsed ultrasonic field absorbs less acoustic energy than that generated by continuous irradiation, i.e. an acoustic clarification effect is shown to exist in a pulsed ultrasonic field. The pulse modulation of an acoustic field decreases the bubble concentration in the cavitation zone. The acoustic power available for each transient bubble is increased and the energy stored by the bubbles during the expansion phase increases too. The decrease of the bubble density decreases the intensity of their interactions and provides the possibility of preserving their shape down to deeper stages of collapse and so the energy concentration in the implosion is increased. This is confirmed by the increase of sonoluminescence intensity in pulsed ultrasonic fields.
