Dr. Gene McHugh
Mountain Time USA
9:00 AM-5:00 PM
© Copyright 2018
DEGREE AND TYPES OF HEARING LOSS
DEGREE OF HEARING LOSS
Results of the audiometric evaluation are plotted on a chart called
an audiogram. Loudness is plotted from top to bottom. Frequency,
from low to high, is plotted from left to right. Hearing loss (HL)
is measured in decibels (dB) and is described in general categories.
Hearing loss is not measured in percentages. The general hearing
loss categories used by most hearing professionals are as follows:
TYPES OF HEARING LOSS:
- Normal hearing (0 to 25 dB HL)
- Mild hearing loss (26 to 40 dB HL)
- Moderate hearing loss (41 to 70 dB HL)
- Severe hearing loss (71 to 90 dB HL)
- Profound hearing loss (greater than 91 dB HL)
The external and the middle ear conduct and transform sound; the
inner ear receives it. When there is a problem in the external or
middle ear, a CONDUCTIVE hearing impairment occurs. When the
problem is in the inner ear, a SENSORINEURAL or hair cell
loss is the result. Difficulty in both the middle and inner
ear is called a MIXED hearing impairment (i.e. conductive
and a sensorineural impairment). CENTRAL hearing loss has more to do
with the brain than the ear, and will be discussed only briefly.
- CONDUCTIVE hearing loss
occurs when sound is not conducted efficiently through the ear
canal, eardrum, or tiny bones of the middle ear, resulting in a
reduction of the loudness of sound that is heard. Conductive losses
may result from earwax blocking the ear canal, fluid in the middle
ear, middle ear infection, obstructions in the ear canal,
perforations (hole) in the eardrum membrane, or disease of any of
the three middle ear bones. A person with a conductive hearing
loss may notice that their ears may seem to feel full or plugged. This person may speak softly because
they hear their own voice quite loudly. Crunchy foods, such as
celery or carrots, sound very loud and this person may have to stop
chewing to hear what is being said. All conductive hearing losses
should be evaluated by an audiologist and a physician to explore
medical and surgical options.
- SENSORINEURAL hearing loss is
the most common type of hearing loss. More than 90 percent of all
hearing aid wearers have sensorineural hearing loss. The most common
causes of sensorineural hearing loss are age related changes and
noise exposure. A sensorineural hearing loss may also result from
disturbance of inner ear circulation, increased inner fluid pressure,
or from disturbances of nerve transmission. Sensorineural hearing
loss is also called "cochlear loss," an "inner ear loss,"
and is also commonly called "nerve loss." Years ago, many
professionals said there was nothing that could be done for
sensorineural hearing loss; that is totally incorrect today. There are many excellent options
for the patient with sensorineural hearing loss.
A person with a sensorineural hearing loss may report that they can
hear people talking, but they can't understand what they are saying.
An increase in the loudness of speech may only add to their
confusion. This person will usually hear better in quiet places and
may have difficulty understanding what is said over the telephone.
- MIXED hearing impairment is
the cumulative effect on conductive hearing loss plus sensorineural hearing
loss. It is typically referred to as mixed hearing loss
with a designated portion attributed to conductive hearing loss.
For example: "35dB mixed hearing loss, with a 20 decibel (dB)
conductive component." By subtraction, one may assume
the remaining 15dB is sensorineural in nature.
- CENTRAL hearing impairment
occurs when auditory centers of the brain are affected by injury,
disease, tumor, hereditary, or unknown causes. Loudness of sound is
not necessarily affected, although understanding of speech, also
thought of as the clarity of speech, may be affected. Certainly
both loudness and clarity may be affected, too. It is believed
most older individuals have some degree of central hearing