10 The Human Ear

  • Human ear is a highly sensitive part of the human body which enables us to hear a sound.
  • It converts the pressure variations in air with audible frequencies into electric signals which travel to the brain via the auditory nerve.

Construction of Human Ear

The ear consists of three compartments:

  • Outer ear
  • Middle ear and
  • Inner ear


  • The outer ear is called ‘pinna’ which collects the sound from the surrounding.
  • The collected sound passes through the auditory canal. At the end of the auditory canal there is a thin membrane which is called as the ear drum or tympanic membrane.
  • When compression of the medium produced due to vibration of the object reaches the eardrum, the pressure on the outside of the membrane increase and forces the eardrum inward.
  • Similarly, the eardrum moves outward when a rarefaction reaches. In this way the ear drum vibrates.


  • The vibrations are amplified several times by three bones in the middle ear:
    • The hammer,
    • The anvil and
    • The stirrup
  • They act as levers.
  • The middle ear transmits the amplified pressure variations received from the sound wave to the inner ear.


  • In the inner ear, the pressure variations are turned into electrical signals by the cochlea.
  • These electrical signals are sent to the brain via the auditory nerve, and the brain interprets them as sound.

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