Our ears are the amazing instruments that have evolved over millions of years that allow us to hear.
The ear is made up of 3 sections: the outer ear, the middle ear and the inner ear.  The auditory nerve connects the inner ear to the brain.

The journey of hearing begins when sound travels through the air as sound waves.   The sound waves reach our outer ear and travel through the ear canal to the ear drum.  The sound waves make the ear drum vibrate and the vibrations pass through the ear drum to the middle ear. 

The middle ear is an air filled cavity with three tiny bones called ossicles.   The vibrations pass through the ossicles to the round window which connects to the inner ear.
The inner ear has two jobs – balance and hearing.

The part of the inner ear involved with hearing is the cochlea.  This is a snail shaped cavity that is filled with fluid and is lined with thousands of minute hair cells or nerve endings.  The vibrations from the middle ear travel through the round window to the fluid of the cochlea.   The tiny hair cells in the fluid transform these vibrations into electrical nerve impulses that are then transmitted by the auditory nerve to the brain.  The brain deciphers these nerve impulses as sounds and gives meaning to the sounds.

In order for you to hear a sound, all the various parts of the ear have to work in sequence to ensure that information gets to the brain.

Hearing impairment or deafness occurs when there is a full or partial reduction in the ability to hear /perceive sounds due to a problem or damage to one or more parts of the ear.

When a hearing loss occurs because of a problem in the outer ear or middle ear, this is called a conductive hearing loss.  Most conductive hearing losses can be treated medically and do not require hearing aids or Cochlear Implants.   Occasionally, if a conductive hearing loss is intractable and ongoing, bone conduction hearing aids may be recommended. Damage to the cochlear or auditory nerve is referred to as a sensorineural hearing loss and is frequently caused by the outer hair cells not working properly.  This type of hearing loss may be addressed with hearing aids or Cochlear Implants, depending on the degree of loss.
In other cases, the outer hair cells may function properly, but the inner hair cells or auditory nerve are damaged, resulting in hearing loss referred to as auditory neuropathy spectrum disorder. 

Degree of hearing impairment:

The degree of hearing loss may be measured as mild, moderate, severe or profound.
Furthermore, a loss of hearing can occur on one side only (unilateral) or on both sides (bilateral) and may be worse in one ear than the other.

Hearing aids amplify sound to allow a person with a hearing impairment to hear clearly.  An audiologist adjusts the intensification of sound of the hearing aid to the individual requirements of the person wearing the hearing aid.  A Cochlear Implant may be recommended when the amplification of the most powerful hearing aids is still not enough to allow a person to hear.

Cochlear Implants bypass the damaged inner ear and sends signals directly to the auditory nerve.  The Cochlear Implant is surgically embedded, with a small microphone placed behind the ear which picks up sound waves and sends them to a receiver that has been placed under the scalp.  The receiver then conveys stimulus directly to the auditory nerve.  These signals are perceived as sound and allow the person to hear.

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