How do the ears work?
Your ears have three sections: the outer ear, the middle ear and the inner ear.
The outer ear
The outer ear consists of the pinna, which is the part you can see on the side of your head, and the external auditory canal, which is the passage that sound travels along. The eardrum covers the other end of the canal. When sound reaches the eardrum from the outside, it vibrates. Beyond the eardrum is the middle ear.
The middle ear
The middle ear is a cavity, filled with air. A chain of three tiny bones, the ossicles stretches right across the middle ear cavity to conduct sound from the eardrum to the inner ear. These three bones are called:
- The malleus – attached to the inside of the eardrum
- The incus – stretching between the malleus and the stapes
- The stapes – the base of the stapes fits into the oval window
When sound enters your ears and makes the eardrum vibrate, the vibrations pass from the eardrum along the ossicles. The stapes pushes like a little piston against the membrane in the oval window of the inner ear. Behind the oval window is the inner ear.
The inner ear
In the inner ear, the cochlea is the hearing part of the ear. The cochlea is a fluid-filled spiral tube. The vibrations caused by sound pass from the stapes through the oval window and into the cochlea. The cochlea is lined with thousands of tiny hair cells. When sound waves enter the cochlea, they move the tiny hairs, causing the hair cells to send electrical messages to the auditory nerve, which sends the information to the brain. Different frequencies (pitches) of sound are picked up by different hair cells, depending on where in the spiral tube they are located. The nerve passes impulses up to your brain, which recognises them as different sounds – for example, people talking, or footsteps.