Skip to content

Hearing

Waves, sound and light · level 3, lesson 6 of 6

A question to start

Your ears can tell a whisper from a shout, and a violin from a drum. How does a wave in the air become a sound you hear?

The idea

Your ear turns the squashes and stretches of a sound wave into signals for your brain.

  1. The outer ear catches the sound and funnels it into the ear canal.
  2. The eardrum, a thin skin across the canal, vibrates as the sound wave hits it.
  3. Three tiny bones pass the vibrations on and make them stronger.
  4. The cochlea, a fluid-filled snail-shaped tube, has thousands of tiny hairs. Different hairs wiggle for different frequencies, and they send signals along a nerve to your brain.
ear canaleardrumbonescochleanerve to brain

Worked examples

1. Two ears. A sound from your left reaches your left ear a tiny moment before your right. Your brain uses that to tell where the sound is coming from.

2. Getting older. The tiny hairs for the highest frequencies wear out first, so older people often cannot hear very high sounds.

3. A cold. When your ear canal and tubes are blocked, the eardrum cannot vibrate freely, and sounds seem muffled.

Try it

  1. Which part of the ear vibrates first when a sound arrives?
  2. What do the three tiny bones do?
  3. What does the cochlea do?
  4. How can you tell which direction a sound comes from?
Answers
  1. The eardrum.
  2. Pass the vibrations on and make them stronger.
  3. Its tiny hairs turn vibrations of different frequencies into signals for the nerve.
  4. It reaches one ear slightly before the other.

Common mistake

"We hear with our outer ears." The outer ear only collects the sound. The hearing happens deep inside, in the cochlea and the brain.

Where it leads