  We study the hydrodynamic interactions between colloids suspended in a
compressible fluid inside a rigid channel. Using lattice-Boltzmann simulations
and a simplified hydrodynamic theory, we find that the diffusive dynamics of
density perturbations (sound) in the confined fluid give rise to particle
correlations of exceptionally long spatial range and algebraic temporal decay.
We examine the effect of these sound-mediated correlations on two-particle
dynamics and on the collective dynamics of a quasi-one-dimensional suspension.
