How Sound are Produced and Propagation
HOW SOUND IS PRODUCED
You hear the sound of your school bell. If you touch a ringing bell of your school you will feel that it is vibrating. Similarly, when a louder sound is emitted by the radio, its cabinet starts vibrating.
For these examples, it is clear that a sound is a form of energy converts into another type of energy. We can say that the molecules of ringing bells move to and fro. They acquire kinetic energy which changes into sound energy.
Whenever there is a strong thunderclap in the clouds, window panes start rattling. The same effect is produced whenever a jet plane crosses the sound barrier and produces explosive sound. These observations also show that sound is a form of energy.
PROPAGATION OF SOUND
Whenever a body is vibrating it produces a disturbance in the surrounding air. This disturbance reaches our earn in the form of waves thus producing the sensation of sound. If there is no medium around the vibrating body, the sound waves will not reach our ears and we will not hear any sound. Let us perform an experiment to demonstrate the above-mentioned fact.
Suspend an electric bell in a bell jar passes its wires through a cork fixed in its mouth as shown in the figure. Switch on the bell. You will hear the sound of the bell. Now start removing air from the bell jar with the help of an exhaust pump. The loudness of the sound decreasing ultimately, although the hammer is still seen striking the bell. This experiment shows that air is necessary for the propagation of sound, in fact, a material medium such as air, water, and metals, etc. Is needed for the sound to travel from one place to another.
When we strike the skin of a drum, It vibrates or moves in and out in a regular pattern Each time when it moves out it causes compression in the air. Each time when it moves in it causes a rarefaction. Because the vibration is regular, so a regular pattern or sound waves of compression and rarefaction travels through the air. These waves on reaching the ear give the sensation of sound.
If you hand a ping pong ball in front of the vibrating drum, you can see the back and forth motion of the ball. This shows that waves are produced by the vibration of the drum skin which produces compression and rarefaction waves (sound waves) These waves travel in all directions.
Some sounds such as the sound of singing a bird, flute, and the tune of a violin have a pleasant effect on the ear and are called musical sounds. Sounds that produce an unpleasant effect on the ear is called noise. The sounds of a donkey, barking dogs, and bomb blast are the example of noise.
Some sounds you hear are loud or faint, some are grave or shrill. The song of a bird is not like the roar of thelion. The sound of the drum is not like that of a violin the sound of a man is not like that of the sound of a woman. Why are these sounds different. These sounds have some characteristics that can make different.