We already have exceeded it.
What happens is a sonic boom.
Sound is a mechanical thing, unlike light. Sound is carried by actual vibrations in actual matter (the medium,) whereas light has no medium whatsoever, unless you prefer the interpretation of light as waves in spacetime itself, which appears to be one way to model it.
The way I see it, and I've studied it, is that electromagnetic waves carry themselves with no medium because it is the give and take of the electric wave with the magnetic wave - one giving when the other is taking and voice-versa - that carries the EM wave along.
Harte
Ok, I'm not thinking clearly. What I meant to ask was what would happen if sound exceeded the speed of light, *IF* it were possible?
Sound waves seem to be very limiting....