1. Sound produced by source travels in a medium in the form of waves.
2. Vibrations produced by source of sound travel by particles of medium.
3. In the case of solids, particles of solid substance vibrates and travel along the substance.
4. In the case liquids, molecules of liquids carry the vibrations for sound propagation.
5. In the case of gas, gaseous molecules act as carries of vibrations and allow the sound propagation.