(a) No, sound cannot travel in vacuum because sound needs a medium to propagate and there are no particles in vacuum to propagate sound.
(b) The speed of sounds differs in different media. The speed of sound is more in solids, less in liquids and least in gases (since solids are much more elastic than liquids and gases). The speed of sound is nearly 5100 m s-1 in steel, 1450 m s-1 in water and 330 m s-1 in air at 0°C.