  We derive the semiclassical equations of motion of a transverse acoustical
wave packet propagating in a phononic crystal subject to slowly varying
perturbations. The formalism gives rise to Berry effect terms in the equations
of motion, manifested as the Rytov polarization rotation law and the
polarization-dependent Hall effect. We show that the formalism is also
applicable to the case of non-periodic inhomogeneous media, yielding explicit
expressions for the Berry effect terms.
