# Physics

### Chapter : 5. Sound

#### Production & Propagation of Sound

Production of sound
Sound is produced when an object vibrates (moves back and forth rapidly). In other word, sound is produced by vibrations of objects.

Propagation of sound
When an object vibrates (and makes sound), then the air layers around it also start vibrating in exactly in the same way and carry sound waves from the sound producing object to our ears. Transmission of sound requires a material medium so it cannot travel through vacuum.
In laboratory a vibrating tuning fork is used for producing sound. During vibration, the prong of the tuning fork moves from one extreme position to another about its mean position (the position when it is at rest).
Let us now see what happens in the air near a vibrating prong of a tuning fork.

SOUND AS A LONGITUDINAL WAVE
When a sound wave travels through the air, the molecules in the air oscillate to and fro about their mean positions in the direction of propagation of the sound wave. Therefore, Sound waves are called longitudinal waves.
The sound waves propagate in any material medium as a series of compressions or rarefactions.

SOUND WAVE CAN BE STUDIED IN TERMS OF PRESSURE AND DENSITY WITH DISTANCE AND TIME.
Pressure & density is high for the particle whose amplitude is less, i.e. at compression state.