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How a normally hearing ear works

The ear is the first part of the hearing system.

Diagram: normal hearing

The pinna is the outer part of the ear that we can see. It gathers sound waves and directs them down the ear canal.

The waves then cause the eardrum to vibrate. These vibrations are passed across the middle ear by three tiny bones. These bones increase the strength of the vibrations before they pass through the oval window into the cochlear.

The cochlea looks like a snail's shell. It is filled with fluid and contains thousands of tiny sound-sensitive hair cells.

As the vibration of the bones in the middle ear enters the cochlea, it causes the fluid to move. This causes the hair cells to bend, which creates a small electrical charge. The charge moves along the auditory nerve to the brain, where it is converted into signals that can be understood.

For us to be able to hear a full range of sounds, all parts of the hearing system must work well. Deafness or hearing impairment happens when at least one part of this system is not working effectively.