Sound waves are longitudinal waves. They cause particles to vibrate parallel to the direction of wave travel. The vibrationsRepeated movements back and forth (about a fixed point). can travel through solids, liquids or gases. The speed of sound depends on the mediumA material through which a wave can聽be transmitted聽(propagate). through which it is travelling. When travelling through air, the speed of sound is about 330 metres per second (m/s). Sound cannot travel through a vacuumA volume that contains no matter. because there are no particles to carry the vibrations.