  A phase transformation in a metastable phase can be affected when it is
subjected to a high intensity ultrasound wave. In this study we determined the
effect of oscillation in pressure and temperature on a phase transformation
using the Gibbs droplet model in a generic format. The developed model is valid
for both equilibrium and non-equilibrium clusters formed through a stationary
or non-stationary process. We validated the underlying model by comparing the
predicted kinetics of water droplet formation from the gas phase against
experimental data in the absence of ultrasound. Our results demonstrated better
agreement with experimental data in comparison with classical nucleation
theory. Then, we determined the thermodynamics and kinetics of nucleation and
the early stage of growth of clusters in an isothermal sonocrystallisation
process. This new contribution shows that the effect of pressure on the
kinetics of nucleation is cluster size-dependent in contrast to classical
nucleation theory.
