Sound is a form of energy which produces a sensation of hearing in our ears.

Production of Sound:

We have produced sound by striking the tuning fork. We can also produce sound by plucking, scratching, rubbing, blowing or shaking different objects.


Vibration means a kind or rapid to and fro motion of an object.

Propagation of Sound:

Sound is produced by vibrating objects. The matter or substance through which sound is transmitted is called a medium. It can be travelled through solid, liquid or gas.

How sound is reaches to human ear?

When an object vibrates, it sets the particles of the medium around it vibrating.The particles do not travel all the way from the vibrating object to the ear. A particle of the medium in contact with the vibrating object is first displaced from its equilibrium position. It then exerts a force on the adjacent particle. As a result of which the adjacent particle gets displaced from its position of rest. After displacing the adjacent particle the first particle comes back to its original position. This process continues in the medium till the sound reaches your ear.

 What happen in Propagation of light?

A wave is a disturbance that moves through a medium when the particles of the medium set neighbouring particles into motion. They in turn produce similar motion in others. The particles of the medium do not move forward themselves, but the disturbance is carried forward. , Hence sound can be visualised as a wave.

Mechanical Waves: Sound waves are characterised by the motion of particles in the medium are called mechanical waves.

Compression: When a vibrating object moves forward, it pushes and compresses the air in front of it creating a region of high pressure. This region is called a compression.

Rarefaction: When the vibrating object moves backwards, it creates a region of low pressure called rarefaction (R).

Compression is the region of high pressure and rarefaction is the region of low pressure.


Sound is a mechanical wave and needs material medium like air, water, steel etc. for its propagation. It cannot travel through vacuum.