Healthy Hearing Program - Special Olympics

Hearing loss can be temporary or permanent, depending on its cause and location in the
ear (see figure 2). A temporary loss can be caused by excessive earwax in the outer ear
canal or congestion in the middle ear (the space behind the eardrum) due to infection.
This is called conductive hearing loss because sound is not conducted efficiently from
the outer to the inner ear. A permanent loss, referred to as sensorineural loss, can result
from viral and bacterial infections, very loud sounds, heredity reasons, syndromes,
medications and a number of other factors. It causes damage to the inner ear’s sensory
structures or the nerve of hearing that connects the inner ear to the brain. A conductive
loss makes sounds too soft to hear comfortably. A sensorineural loss does the same, but
often makes sounds unclear as well, no matter how loud.
Figure 2:
Anatomy of the ear.
Reprinted with permission from
CIBA-GEIGY, 2001
How is hearing acuity measured?
Hearing acuity can be measured on a decibel (dB) intensity scale from 0dB (no hearing
loss) to 110dB (maximum hearing loss), based on normative study data. Threshold
values are usually assessed for specific test frequencies that range from low to high
(125 hertz (Hz) through 8000 Hz). Pure tone audiometers, calibrated for intensity
and frequency, are used to measure hearing acuity. Some audiometers also permit the
evaluation of a hearing threshold for speech based on normative data. Threshold
measurements for pure tones and speech require extremely quiet surroundings, often
prefabricated test rooms meeting specific standards for noise reduction.
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