Assuming the model of a sigle free cavity in an incompressible, inviscid liquid, a threshold energy for the transient cavitation is obtained as a function of the rest radius of the cavity. The comparison with available experimental data from laser induced cavitation bubbles was carried out, and it gave satisfactory agreement with experiment. Moreover, considering the energy per unit mass of the cavity content at collapse, a simple explanation of the absence of cavitation effects above about 2.5 MHz of the driving field is found.