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How We Hear

Read this page to learn how we hear sound.

First, here are the parts of the ear:

• The outer ear
  • The outer ear is made up of the ear flap and the ear canal up to the eardrum.
  • The ear flap is also called the auricle or pinna.
  • The ear drum is also called the tympanic membrane.
  • The outer ear protects the middle and inner ears.

Image courtesy of EDEN - The Electronic Deaf Education Network (a) Outer ear   (b) ear canal    (c) eardrum (d) hammer, anvil and stirrup   (e) cochlea   (f) auditory nerve



• The middle ear
  • The middle ear is made up of three tiny bones and the Eustachian tube.
  • The Eustachian tube connects the middle ear to the back of the throat. It opens and closes to make the pressure between the inner and outer ears the same.
  • Three tiny bones connect the ear drum to the inner ear. The bones are called the hammer (malleus), anvil (incus) and stirrup (stapes).
• The inner ear
  • The inner ear is made of the vestibular apparatus and the cochlea.
  • The vestibular apparatus is three looping canals. They control your balance.
  • The cochlea turns sound into electrical signals that get sent to the brain. The cochlea is spiral-shaped.

Now, here's how sounds get from the outside to our brains.

1. Sound moves from the outside to your outer ear.
   • The outer ear passes sound to the middle ear.
2. Your middle ear passes sound to your inner ear.
   • Sound makes your eardrum vibrate like a drum.
   • The vibrations pass to the three tiny bones behind the eardrum. (These are the hammer, anvil and stirrup.)
   • The bones pass the vibrations to the inner ear.
3. The vibrations go to the cochlea in your inner ear.
   • Tiny hair cells in the cochlea pick up the vibrations.
   • The hair cells turn the vibrations into electrical signals.
   • The electrical signals are sent to the auditory nerve, and then the brain.
4. Your brain decides what the sound is.
   • The auditory cortex is the part of the brain where the signals are put with other information. The other information could be what you see, and your memories.
   • This helps us to "know" what we're hearing. (For example, you hear a car honk and think, "That's a car honking.")

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