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Study of 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.  

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.  

We are able to hear the bursting of crackers even when we are standing at a distance. How is it possible? How does the sound produced by a cracker reach us?

The sound of a bursting cracker reaches us through air. It shows that sound can travel through air.

Let us try to understand this better.

A material medium is necessary for the propagation of sound. Vacuum is devoid of any material. Hence, sound cannot travel through vacuum.

Outer space is devoid of any material medium. Hence, no sound can be heard in outer spaces. To communicate in such areas, astronauts use walkie-talkies. A walkie-talkie is an instrument, which uses radio waves for the transportation of messages.

Can sound travel through liquids?

To find out whether sound can travel through liquids, let us perform the following activity.

Take a metal plate and spoon. Place them inside a bucket filled with water. Hit the plate with the spoon in such a way that it does not touch the body of the bucket.

Now, carefully place your ear near the surface of water. Are you able to hear the sound produced?

You can hear the produced sound. Sound reaches your ear after travelling through water. Hence, we can say that sound travels through liquids.

Dolphins communicate with each other by sending high pitched squalls. It shows that sound can travel through water.

Can sound travel through solids?

Place your ear on one end of a long table. Ask your friend to tap the table from the other end. Do you hear any sound?

You can hear the produced sound. Sound reaches your ear after travelling through the table. This indicates that sound can travel through solids.

Stethoscope is an example of sound travelling through solids. Doctors use stethoscopes to listen to your heartbeat.

Sound can travel in solids, liquids, and gases. However, sound cannot travel in vacuum.

The Human Ear

We have two ears to hear the different sounds that are around us—the soft purring of a cat, the loud barking of a dog, the tinkling of a bell, the blaring of a horn, etc. Our ears detect all types of sounds lying in the hearing range and send sound signals to the brain. In this lesson, we will learn about the working of the human ear.

Structure of the Human Ear

The ear is one of the five sensory organs of the human body. It can sense sound waves from various sources. Take a look at this figure to know the various parts of the human ear.

The Human Ear

The human ear consists of three main parts—the outer ear, the middle ear and the inner ear. The following chart shows these three parts and their sub-parts.

 

The eardrum is the intersection of the outer ear and the middle ear. The oval window is the intersection of the middle ear and the inner ear.

The stirrup bone of the middle ear is the smallest bone in the human body.

Parts of the Human Ear with Their Functions

The following table lists the functions of the different parts of the human ear.

Ear parts

Sub-parts

Functions

Outer ear

Pinna

Collects and sends sound to the ear canal

Ear canal

Provides passage for sound to reach the eardrum

Eardrum or tympanic membrane

Vibrates in response to sound; very sensitive membrane

Middle ear

Middle ear bones

Transfer sound energy to the cochlea

Eustachian tube

Connects the middle ear to the throat

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