  Convective instabilities in the advanced stages of nuclear shell burning can
play an important role in neutrino-driven supernova explosions. In our previous
work, we studied the interaction of vorticity and entropy waves with the
supernova shock using a linear perturbations theory. In this paper, we extend
our work by studying the effect of acoustic waves. As the acoustic waves cross
the shock, the perturbed shock induces a field of entropy and vorticity waves
in the post-shock flow. We find that, even when the upstream flow is assumed to
be dominated by sonic perturbations, the shock-generated vorticity waves
contain most of the turbulent kinetic energy in the post-shock region, while
the entropy waves produced behind the shock are responsible for most of the
density perturbations. The entropy perturbations are expected to become buoyant
as a response to the gravity force and then generate additional turbulence in
the post-shock region. This leads to a modest reduction of the critical
neutrino luminosity necessary for producing an explosion, which we estimate to
be less than $ \sim 5 \% $.
