Sound is a form of energy which produces the sensation of hearing. With sound energy is transferred from one place to another. The sound is produced by vibrating bodies. A sound progressive the particles of the medium are sent into vibration thus transferring energy.
The sound is a mechanical wave. It cannot travel through vacuum. It essentially requires a medium for its propagation. The sound travels faster in a denser medium. Thus the speed of sound in water is more than in air. It travels faster in solid than water.
Sound can be reflected light light from the surface of a solid. The laws of reflection followed by sound are same as light:
1st : the angle of incidence is always equal to the angle of reflection.
2nd : the incident soundwave, the reflected sound wave and the normal to the reflecting surface at the point of incidence all lie in the same plane.
There are three types of sound:-
1st : Infrasonic sound - range below 20 Hertz
Which we can't hear as it is below our hearing range.
2nd : Audible sound - range between 20 Hertz to 20000 Hertz
Which we can hear as it is our hearing range.
3rd : Ultrasonic sound - range above 20000 Hertz
Which we can't hear as it is above our hearing range. This sound is produced by bats while flying.
Sound needs medium to travel it can be proved by an activity :-
Take an electric bell and an airtight glass bell jar. The bell jar is connected to a vaccum pump. Of you press the switch you will be able to hear the bell. Now start the vaccum pump. When the air in the jar is pumped out gradually, the sound became fainter, although the same current is passing through the bell. After some time when less air is left inside the bell jar you will hear a very feeble sound.
