- The human ear is designed
to pick up a wide range of acoustic stimuli from the
environment, process it, and transfer it via specialized
neurons (nerve cells) to our brain, where it is analyzed
into what we perceive as sound.
- Our ability to hear sounds over
time may diminish as a result of use and abuse, trauma (ear
drum perforation), or injury to the ear (e.g., infections).
- The ear is composed of 3 parts: the
outer, the middle, and inner ear. The outer ear
consists of the pinna and the ear canal.
- From the pinna, sound enters the
ear canal and hits the eardrum (separating the outer ear
from the middle ear), which increases the volume of certain
pitches.
- Transmitting sound across the middle
ear to the inner ear are three tiny bones, ossicles, of the
middle ear, shaped like a hammer, anvil, and stirrup.
The ossicles pass and amplify vibrations from the eardrum to
the cochlea (a structure shaped like a snail's shell)
which is a part of the inner ear.
- After reaching the cochlea,
vibrations set tiny hair cells in motion, which transform
the vibrations into electrical signals that are picked up by
the acoustic nerve and transmitted to the brain.
- The eustachian tube connects the
nose and throat to the middle ear. Consequently,
allergies, throat infection, and sinus problems may have an
adverse effect on the middle ear function as well.
- If there is damage to the ear canal
or the middle ear (e.g., wax build-up, perforated eardrum,
damaged ossicles), sound cannot travel to the cochlea,
causing what is known as conductive hearing loss.
- Sensorineural hearing loss occurs
most commonly as a result of damage to or aging of the inner
ear structures.
- Exposure to loud sounds can damage
the hair cells and interfere with the normal transmission of
nerve impulses to the brain and hearing, especially in
occupations involving prolonged exposure to high decibel
pollution (e.g., factory workers, rock and roll musicians,
explosives experts, etc.).
- Hair cells can also be affected by
infection (e.g., viral) or as the result of normal aging.
With this type of hearing loss, our ability to discriminate
between sounds is affected and the conversation of others
will be difficult to understand.
- Mixed hearing loss is caused by
both conductive and sensorineural impairments.
- Any type of hearing loss needs an evaluation by an ENT (Ear, Nose, and Throat) physician, and testing by an audiologist.
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