The human ear is an intricate and delicate part of our bodies. Exactly how does it work? How does it transmit sound?
A normally functioning ear transmits sound in the following way:
Sound is transmitted as sound waves through the ear canal to the eardrum.
As the ear drum vibrates in response to these sound waves it causes the three tiny bones of the middle ear (hammer, anvil and stirrup) to vibrate.
The vibrations continue through the middle ear bones and across a tiny membrane to the fluid in the snail- shaped inner ear called the cochlea.
Fluid movement causes thousands of tiny hair cells in the cochlea to move.
The movement of the hair cells converts the fluid movement into electric energy.
The electrical energy is transmitted by the hair cells to the hearing (auditory)nerve.
The auditory nerve sends the electrical impulses to the brain where they are interpreted as sound.
Unfortunately, “normal” hearing function is not the standard for a large percentage of our population. Hearing impairment affects about one in 10 Americans. Hearing loss can be conductive (due to faulty transmission of sound waves) or sensorineural (faulty sound reception by nerve cells), or both.
Common causes of conductive hearing loss are wax blocking the ear, a perforated eardrum, or fluid in the ears.
Common reasons for sensorineural deafness are noise exposure, age-related changes, and ototoxic drugs (those that are known to damage hearing).
Sound levels are measured in decibels. Decibels are like the degrees of a thermometer. As temperature increases, so do the number of degrees. As the volume of sound increases, so do the number of decibels.
Normal conversation is usually between 45 - 55 dB. A baby crying hovers around 60 dB and downtown traffic can blister the ear at 90 dB.
Hearing loss can be:
Mild (a loss up to 40 dB) - with trouble in hearing ordinary conversation
Moderate (40-60 dB) - where voices must be raised to be heard
Severe (over 60 dB loss) - where people must shout to be heard
According to the World Health Organization, the term "deaf" should only be applied to individuals with hearing impairment so severe that they cannot benefit from sound amplification or hearing aid assistance.
