Figure 7.

Variation of subharmonic response (a) with ambient over-pressure for free bubbles of radius $R_0^0=0\mathrm{.}5\mathrm{,}1\mathrm{,}1\mathrm{.}5\mathrm{,}2\mathrm{,}2\mathrm{.}5\mathrm{,}3\mathrm{,}4$, and $5\mu \mathrm{m}$ at excitation frequencies such that $f=2.5f_0^0$, (b) with excitation pressure for a free bubble of $R_0^0=2\mu \mathrm{m}$ at $f=4.3784\mathrm{MHz}\mathrm{=}2.5f_0^0$, (c) with ambient pressure for a free bubble of $R_0^0=2\mu \mathrm{m}$ at fixed excitation frequency $(f=4.3784\mathrm{MHz}\mathrm{=}2.5f_0^0)$ and different excitation pressures, and (d) with ambient pressure for a free bubble of $R_0^0=2\mu \mathrm{m}$ at different excitation frequencies.