Sound is a mechanical wave that results from the back and forth vibration of the particles of the medium through which the sound wave is moving. In physics, the sound is a vibration that propagates as an acoustic wave, through a transmission medium such as a gas, liquid or solid. In human physiology and psychology, the sound is the reception of such waves and their perception by the brain. Sound is created when something vibrates and sends waves of energy (vibration) into our ears—the more robust the beatings, the louder the sound. Sounds are fainter the further you get from the sound source.