How the ear works
The ear is made up of three parts - the outer ear, the middle ear and the inner ear.
The outer ear
The outer ear is also known as the auricle or pinna and is made of cartilage. It is the part of the ear, which is visible. It collects sound waves and channels them into the ear canal, where the sound is amplified. At the end of the canal is the eardrum, which separates the outer ear from the middle ear. When the sound waves reach the eardrum it vibrates.
The middle ear
The middle ear, an air-filled cavity, contains three bones - the hammer, anvil and stirrup - which are physically connected to each other. The hammer is connected to the eardrum and it moves in response to vibration of the eardrum. The hammer in turn causes movement of the other two bones. This process amplifies the sound and transmits it on to the inner ear.
The middle ear is connected to the back of the throat via the Eustachian tube. This tube is important in equalising air pressures between the middle ear and the external air. Differences in these air pressures across the eardrum can reduce hearing.
The inner ear
The inner ear contains the cochlea; a snail-shell shaped structure filled with fluid and lined with tiny hair cells. The movement of the stirrup in the middle ear presses a window like membrane on the surface of the cochlea. As the hair cells are stimulated, they convert the sound waves into electrical impulses. These electrical impulses are transmitted through the auditory nerve to the brain where the signal is interpreted as the perception we know as sound.
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