  We consider acoustic propagation in an irrotational vortex, using the
technical machinery of differential geometry to investigate the ``acoustic
geometry'' that is probed by the sound waves. The acoustic space-time curvature
of a constant circulation hydrodynamical vortex leads to deflection of phonons
at appreciable distances from the vortex core. The scattering angle for phonon
rays is shown to be quadratic in the small quantity $\Gamma/(2\pi cb)$, where
$\Gamma$ is the vortex circulation, $c$ the speed of sound, and $b$ the impact
parameter.

Condensed Matter;General Relativity and Quantum Cosmology