Velocity of sound varies as the inverse of the square root of the
density of the medium it is in. The speed also then will depend on the
temperature of the medium too. For steel is it about 4870 m/sec. As a
reference, the speed of sound in air is about 340 m/sec. (Both numbers
are for room tempurature). The second question is more interesting.
Unlike light, sounds needs some kind of material to propogate through.
In a vacuum there is nothing, so sound cannot go through a vacuum.
(published on 10/22/2007)
