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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.
 

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

Inner ear

Semi-circular canals

Send messages to the brain for balancing

Cochlea

Sends sound messages in the form of electrical impulses to the brain

Auditory nerve

Conducts electrical messages to the brain where sound is then heard

 

Working of the Human Ear

Know More

The cochlea is a circular or snail-shaped, fluid-filled bone containing hair cells. Sound vibrations in the cochlea cause the hair cells to bend. As a result, electrical impulses get generated. These are then are carried to the brain by the auditory nerve. Consequently, sound is heard.

The Eustachian tube allows the middle ear fluids to drain and enables air to enter it from the throat.

Hearing Loss

Sounds above 85 dB can damage the eardrum. This may lead to hearing loss. Decibel (dB) is the unit of the intensity of sound. The following table lists the intensity of sound corresponding to various sounds and sources of sound.

Sources of sound

Intensity levels (dB)

Blowing leaves

10

Whisper

20

Mosquito buzz

40

Normal conversation

60

Busy city traffic

80

Large orchestra

100

Leaf blower

110

Jackhammer

120

Jet plane

140

The diaphragm of the eardrum may break or perforate at the sound intensity level equal to or greater than …

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