Everybody knows whether a sound is pleasant or unpleasant, loud or soft, mellow or sharp, but few people can actually explain what sound is and what are it qualities.
The string of a guitar or a harp is silent until it is plucked with the finger or a plectrum and set into vibration. The skin of a drum does not produce any sound until it is struck with a drumstick and made to vibrate. The sound of the saxophone is also produced by the vibration of its red. In a trumpet the noise comes from air that is thrust into the instruments and vibrated.
All sounds—the human voice, the noises made by animals, the tinkling of a bell or the buzzing of insects –is the result of vibration. Scientists have also discovered that there can be sound if there is no air to be vibrated.
An experiment was once carried out in which a bell was placed inside a glass jar. As soon as all the air was removed from the jar the ringing of the bell could no longer be heard.
Astronauts have confirmed that there is absolute silence in space.
It is easy, therefore, to see that sound spreads through the atmosphere like waves or ripples that spread outwards in a pond when something drops into it.
Picture Credit : Google