Sound is a form of energy which produces the sensation of hearing in our ears. All sounds are produced by vibrations of substances. These vibrations travel as disturbances in a medium and reach our ears as sound. The human ear can hear only a particular range of frequency of sound, and only within a certain range of energy.
1. Production and Propagation of Sound
Production
When a tuning fork is struck on a rubber pad, it starts vibrating. These vibrations cause the nearby molecules to vibrate. Thus, vibrations produce sound.
Sound Needs a Medium
- Sound needs a material medium like air, water, steel etc. for its propagation.
- It cannot travel through vacuum. This is demonstrated by the Bell-Jar experiment.
- In this experiment an electric bell is suspended inside an airtight glass jar connected to a vacuum pump. As the air is pumped out, the sound becomes feebler and feebler. No sound is heard when the air is fully removed (the jar has vacuum).