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The outer ear collects sound and channels it down the ear canal to the eardrum. The sound makes the eardrum vibrate, and it passes those vibrations into the middle ear.

In the middle ear three small bones, the malleus, incus and stapes, pick up the vibrations and make them stronger (they amplify them).

The vibrations reach the cochlea in the inner ear: a snail-shaped tube filled with fluid. The fluid ripples and makes a wave along the basilar membrane. Hair cells sitting on it move with the wave. Hair cells near the wide end detect high-pitched sounds; those near the centre detect low-pitched sounds.

Experiment: Where is that sound?

1. The listener sits on the chair with eyes closed.
2. The tester stands about 2 m away, in a direction they choose secretly (left, right, in front or behind), and taps the pencils together once.
3. The listener points to where the sound came from. Record if they were right.
4. Do 10 taps from mixed directions. Keep it fair: same distance, same tap, same listener.
5. Now the listener gently covers one ear with a flat hand. Do 10 more taps.
6. Compare the scores. Then swap jobs.

Test	Correct (out of 10)	Most mistakes were…
Both ears
Left ear covered
Right ear covered

Questions

1. Describe the journey of a sound from the air to your brain. Use: eardrum, three bones, cochlea, hair cells, nerve.

2. Your results: how many correct with both ears, and with one ear covered?

3. Why did covering one ear make finding the sound harder?

4. Give two ways to protect your hearing.

Sources for every fact on this sheet: echoesof.science/school/ears/sources/

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