Again recent research suggests that the universe will continue to expand, growing infinitely large. Sound waves would be affected because as space expands, the density changes. Since, sound waves are dependant on the density of the medium they would be affected, although in a very complicated manner. Gravity waves should indicate the expansion of space, in the same way that electromagnetic waves do, since they travel at the speed of light. However, these waves have not yet been directly detected.
Gravity is the only force that has been shown to retard or prevent expansion.
For example, space within our solar system, indeed within our galaxy is not expanding. This is due to the intense force of gravity, near large amounts of mass. Only at a certain distance from large masses will the driving force of expansion be able to overcome the effects of gravity. However, the curvature of space due to gravity has nothing to do with expansion. The curvature due to gravity is a geometrical concept describing gravity, not a physical reality.