Sound

Production of sound

If somebody calls you from behind, you will quickly turn around. What makes you do so?

We turn back in response to a call because of the sound heard by us. We are able to talk to each other because of the sound produced by us. We are able to predict the distance of a train only by listening to the sound it produces. Similarly, we can distinguish between different musical instruments because of the sounds they produce.

How do you realize that an alarm bell is ringing?

So, what is sound?

Sound is a form energy that produces the sensation of hearing in our ears and vibrating bodies produce sound. 

Do you know how a sound is produced? To find out, let us perform the following activities.

Take a frying pan and suspend it in air with the help of support. Hit the pan with a metal spoon. Now, touch the pan. Can you feel the vibrations? When you beat an object, you can feel its vibrations with the help of your sense of touch. Touch the pan when it is not producing any sound. Can you feel the vibrations now?

 

 

 

Take a rubber band and stretch it between two poles (as shown in the given figure). Now, pluck the rubber band in the middle. Can you hear any sound? Does the rubber band vibrate when it produces a sound? On plucking a stretched rubber band or a stretched string, it vibrates rapidly and produces a sound.

 

 

Take a cooking utensil and pour some water in it. Now, beat the utensil with a rod. You will hear a sound. Carefully, observe the surface of water in the utensil. Do you see concentric circles moving on the water surface? These are vibrations in water, produced by vibrations of the utensil body, on beating.

Therefore, it can be concluded that a vibrating body produces sound.

The back and forth movement of an object produces sound. An object moving back and forth is said to be in vibration. Hence, sound is produced by vibrating objects.
 

While watching a group of children playing hide and seek, Himesh observed how a blind-folded boy was able to catch the other children by hearing the sounds produced by them. This made him wonder how sounds are produced by humans.

While singing a song, put your hand on your throat. You will find a part of your throat moving up and down. This part of your throat is known as the voice box or larynx. The larynx is responsible for producing sounds in humans. It moves when we swallow something.

We know that a vibrating object produces sound. Then, which part of our body vibrates to produce sounds?

The voice box consists of two vocal chords. These chords are arranged in such a manner that there is a small gap between them. This small gap allows air to pass through. When we speak, air is forced into this small gap by the lungs. This prompts our vocal chords to vibrate and hence, produce sounds.

Let us understand better by performing a small activity. Take a piece of paper and cut two small rectangles out of it. Now, put these two pieces of paper one above the other such that there is a small gap between them.

Now, blow air through this small gap. Can you hear a sound? Your voice box functions in the …