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Hearing and the ear
How does the ear work?
Hearing loss

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Over one million Australians have some kind of hearing loss. Of these over 50 000 have severe or profound deafness and can hear virtually no sound. Three in every 1000 children are born with a hearing loss or develop a loss before learning to speak.

How does the ear work?
Diagram of the ear
Diagram of the ear
Courtesy: Department of Otolaryngology, The University of Melbourne

Hearing occurs when sound waves are collected by the ear as vibrations which are passed to the cochlea where they are transmitted as electrical signals which are then decoded by the brain.

The ear has three parts, the external, middle and inner ear. The external ear is made up of the pinna (the fleshy part on the side of your head) and the ear hole or ear canal. The pinna collects the sound and directs it into the ear canal towards the ear drum membrane.

The ear drum is the start of the middle ear, and vibrates when sound hits it. The vibrations from the ear drum are passed onto three small bones (the smallest in the body) called the ossicles. These middle ear bones amplify the sounds and pass them into the inner ear.

The inner ear contains the shell like structure called the cochlea, which transfers the vibrations along the auditory nerve using electrical signals that are perceived by the brain. The "nerve fibres at the entrance to the cochlea typically respond to high frequencies of sound, while those at the end of the cochlea respond to low frequencies". (Cochlear, 2001)

Hearing loss
Deafness or hearing loss occurs when something goes wrong with some part of the ear. It is detected when a listener is unable to receive or interpret sounds. There are two basic types of deafness:

  • conductive
  • sensori-neural.

Conductive deafness occurs when sound is prevented from reaching the inner ear. This can happen when the ear drum is perforated by an infection or the ossicles become stiff. In this case the inner ear is normal and the sound is prevented from getting to the cochlea.

In sensori-neural deafness there is a problem with either the cochlea or the transmission of the signals to the brain once they have left the cochlea. This can be caused by exposure to loud sounds such as music or construction sites.

The cochlear implant system can help people with sensori-neural deafness.

For more information about hearing loss visit
Better Hearing Australia, a support organisation for people with hearing loss.
National Occupational Health and Safety Commission

If you listen to loud music you might want to check
Hearing Education and Awareness for Rockers.

For more information about hearing:
NOVA: Science in the News: includes info on the mathematics of hearing.
Cochlear Ltd

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