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We hear a different kinds of sounds in our daily life. The thundering of clouds, chirping of birds, the mewing of cats, rustling leaves, music on the radio and television and noise of vehicles are some of the sounds that all of us are familiar with. Each sound has particular characteristics. We make sounds to communicate with one another. Animals also communicate with other members of their species with the help of sound. Some sounds like music are pleasing to us, and we like to hear them. But some sounds, for example, noise in our surroundings, is undesired. In this lesson, we will study the production and propagation of sound, human voice system, hearing, noise pollution and the ways to control it.
Different kinds
of sounds
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Production of sound:
Sound is produced by vibrating bodies. It is measured in \(decibels\)(\(dB\))
What is vibration?
Vibration means a kind of rapid to and fro motion of a particle. This to and fro motion of the particle causes the substances around it to vibrate. Thus, sound spreads to the surroundings.
Sound 8th.png
Vibration/sound produced by pan
The above image shows the production of sound when the boy hits the pan with a stick. When we touch the pan, we can feel the vibration.
The substance through which sound energy is transmitted is called a medium. Sound travels through a medium from the point of origin to the listener.
Let us understand the production of sound with the help of following activity.
When you pluck a rubber band, it begins to vibrate. You can hear a weak humming sound as long as the rubber band is vibrating. The humming sound stops when the rubber band stops vibrating. This confirms that sound is produced by vibrating particles. You can see this kind of vibrations in stringed musical instruments, such as guitar and sitar. In some cases, the vibrations are visible.
Could you think of any such cases?