Beaumont Hospital

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Understanding Hearing Loss

Understanding Hearing Loss

The ear has three parts: the outer ear, middle ear, and inner ear.  The inner ear houses the hearing organ called the cochlea.  The auditory nerve makes connection with the cochlea and sends sounds to the most important part of the auditory system, the brain.  The process of hearing occurs when sound waves travel through the air and are picked up by the outer ear. The sounds are funneled down the ear canal, where they make the eardrum and the three little bones in the middle ear vibrate. These vibrations are then passed into the inner ear and to the cochlea. Thousands of tiny hair cells in the cochlea sense the vibrations and trigger an electrical message to be sent to the auditory nerve which then sends the electrical signal to the brain.  The brain interprets the signal as sound. 

 Earsignal

What happens when someone has a hearing loss? 

There are lots of different causes of hearing loss.  Some people have problems in the outer or middle ear, these are referred to as conductive hearing loss.  Individuals with this type of hearing loss can usually be helped surgically (e.g. grommets, stapedectomy), or with a good hearing aid, so that they do not need a cochlear implant. However, those people who have problems in their inner ear because the hair cells are damaged or absent, have a sensori-neural hearing loss.

When there is only some of those hair cells missing or damaged, a hearing aid can be enormously useful. Where the damage is more severe, there may not be enough hair cells left to pick up the amplified signal provided by a hearing aid.  For these people a cochlear implant may be of more benefit.