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So far, we have learned that vibrating objects produce sound, which travels in all directions through a medium. How do we hear it?
How do we hear a sound?
The outer part of the ear is shaped like a funnel. When sound enters, it travels down a canal until it reaches the end, where a thin membrane is stretched taut. we call it as eardrum.
Let us discuss a tin can model of the eardrum to better understand what it does.
  1. Take a tin can, and cut the ends off of it.
  2. Using a rubber band, cover a piece of rubber balloon across one end of the can.
  3. Place four or five dry cereal grains on the stretched rubber.
  4. Now ask your friend to speak "Hurrey, Hurrey" from the open end.
  5. Observe what happens to the grain.
The grains that placed over the balloon moves up and down when your friend speaks at the open end of the tin, which shows that sound travels in the form of waves and, when it hits the rubber sets it to vibrate. Our eardrum also works in the same form.
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Experiment on vibration
Structure of Human ear:
The ear is the organ of the human body that enables us to hear different sounds around us. It can be divided into three main parts:
  • Outer ear
  • Middle ear and
  • Inner ear
Outer ear:
  • This is the outermost visible part of the human ear.
  • The outer ear gathers sound waves and forwards them towards the ear canal.
  • At the end of the ear canal lies the eardrum. Sound waves travel through the ear canal and strike the eardrum.
Middle ear:
  • The eardrum is made up of a membrane, which starts vibrating with the frequency of the sound wave that falls on it. The ear drum transforms the sound waves into vibrations that then travel to the inner ear.
  • The eardrum is a thin rubber-like sheet present in the Middle ear.
  • The eardrum vibrates as a sound wave reach it, and these vibrations propagate to the inner ear.
Inner ear (Cochlea):
  • Inner ear (cochlea) receives the vibrations sent by the eardrum.
  • The inner ear contains a liquid-like substance through which the vibrations can travel.
  • The inner ear has tiny hairs that turn the vibrations into signals. It is then, the brain receives the signals through the hearing nerve.
  • When the brain receives the signal, it interprets the sound instantaneously. However, the whole process is so quick that we cannot notice it.
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Interior view of human ear