  We study the oscillation spectrum and acoustic properties of a liquid drop in
the phase-separated fluid when the interfacial dynamics of phase conversion can
be described in terms of the kinetic growth coefficient. For a readily mobile
interface, i.e., as the growth coefficient becomes comparable with a reciprocal
of the acoustic impedance, anomalous behavior is found in the oscillation
spectrum of a drop as well as in the velocity and absorption of a sound wave
propagating through a suspension of drops in the two-phase system. Compared
with the known case of two immiscible fluids, the high interface mobility leads
to an anomalous softening of the radial drop pulsations and to the frequency-
and temperature-dependent behavior for the sound velocity and absorption
coefficient in a two-phase suspension.
