Sound

Sound is the vibration of any substance. The substance can be air, water, wood, or any other material, and in fact the only place in which sound cannot travel is a vacuum. When these substances vibrate, or rapidly move back and forth, they produce sound.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.
Properties of Sound Waves :
Sound is produced by vibration. For example when we speak our voice creates vibration in air near to it. In music instrument (like Sitar, Tabla, Gitar etc.) the second is produced due to vibration created in air by vibrating string strings or membranes.)
Sound waves are mechanical in nature, hence they need materialistic medium to travel. Sound wave can travel in liquid, solid and gas but to in vacuum.
Sound waves are longitudinal in nature. Hence when it travels compression and rarefaction pulses are produced in medium in the direction of sound propagation.
Sound waves are longitudinal in nature. Hence when it travels compression and refraction pulses are produced in medium in the direction of sound propagation.