How does your hearing work?
Monday, January 13, 2014
Your ear is made up of three main parts: the outer ear, the middle ear and the inner ear. You can see most of the outer ear, called the pinna or auricle, which then leads to the ear canal and ends with the eardrum. Behind the eardrum is the middle ear: an air-filled space that contains three tiny bones called the ossicles. Beyond that is the inner ear which contains the cochlea and hearing nerve.
When sound reaches the outer ear it is funneled into the canal by the pinna. Those sound waves then reach the eardrum and cause it to vibrate, just like the head of a drum does when it is struck. The vibrations from the eardrum then travel along the chain of bones, or ossicles, within the middle ear. Then the vibrations finally reach the cochlea in the inner ear. The cochlea contains fluid which surrounds the hair cells or nerve endings. As the vibrations create a wave in the fluid of the cochlea, the nerve endings are stimulated according to pitch, like hitting a particular note on a piano.
A blockage or illness in either the outer or middle ear will result in a "conductive" hearing loss. Sound is not allowed to travel through these spaces correctly so the sound is much softer by the time it reaches the nerves. This could be a temporary hearing loss caused by wax or other foreign object in the ear canal, an infection in the ear canal (swimmer's ear) or middle ear, or a hole (perforation) in the ear drum. It could also be permanent caused by a congenital deformity (something you are born with), damage to the eardrum or ossicles from chronic or untreated ear infections or head trauma from injury.
Damage to the inner ear is called a "sensorineural" hearing loss. This is most often permanent and can be caused by noise exposure, genetics, age, viral infection or high fever, or very strong "ototoxic" medications.
Some people will have a combination of a conductive hearing loss and sensorineural loss. This is called a mixed hearing loss, when the outer or middle ear space and the nerve both have a hearing impairment. An evaluation by an Audiologist will determine the type and degree of hearing loss that you have and recommend the next course of action appropriate for your hearing needs.
If the hearing loss is sensorineural, related to the nerve, medical or surgical treatments are usually not corrective options. Hearing aids are most often the best treatment to help correct for the hearing loss. An Audiologist is the best professional to see to determine the best amplification for your needs. If the hearing loss is conductive, an Ear, Nose and Throat physician should be consulted to see if medical treatment is indicated. If they determine that there is not a feasible medical option, then an Audiologist can again determine the best hearing aid option for your needs.