CLASSIFICATION OF SOUND WAVES

Sound waves can be classified into following three classes:

1.       Audible waves

2.       Infrasonic waves

3.       Ultrasonic waves

Audible waves:

The waves which can be heard by human ears are called audible waves. Their frequency range extends from 20 Hz to 20 KHz but it may vary from person to person in accordance to his age. Children and youth can hear sounds of up to 20 KHz frequency whereas the audible range of old persons is lesser than 20 KHz.

Infrasonic waves: 

Waves having a frequency of less than 20 Hz are called infrasonic waves. These waves cannot be heard by human ears. These waves are produced by the vibration of huge bodies like the earth.

Ultrasonic waves:

Waves having frequency of more than 20 KHz are called ultrasonic waves. These waves also cannot be heard by human ears, but can be heard by bats. The bat can hear waves of frequencies up to 50 to 60 KHz and can produce such waves even.

These waves have proved to be very useful to mankind. These are used for communications and for the determination of depth of sea. Besides it, these are used for increasing agricultural yields, for improving the quality of seeds, for protection against insects and in the field of treatment especially surgery.

ARTICULATION OF SOUND

 Articulation or modification of sound is necessary before broadcasting. For this, the following instructions should be observed:

1.       The broadcasting room should be perfectly sound-proof so that unwanted sounds may not enter in the room.

2.       Microphone, record player, tape recorder and amplifier etc. should have a high efficiently so that all the fundamental and harmonic frequencies remain undistorted.

3.       The frequency range of sound is limited between 30 Hz to 12 KHz since the frequency of all sounds produced by man, sound and musical instruments lies between 30 Hz to 12 KHz. By limiting the frequency range, amplification of high quality and high fidelity is easily possible.

4.       Before sending the sound signals to the transmitter they should be amplified up to a required level.