Encyclopedia of Health and Medicine

audiologic assessment 9
quencies of normal conversation, the loss, though
gradual, becomes apparent. Hearing aids that
amplify sound waves in these frequencies can help
restore the function of hearing. OTOSCLEROSIS
(fusion of the auditory ossicles, the tiny bones of
the inner ear) and damage to tissues that results
from impaired blood circulation (caused by ATHER-
OSCLEROSIS, for example) also diminish hearing.
See also BRAIN; EUSTACHIAN TUBE; GENERATIONAL
HEALTH-CARE PERSPECTIVES; NUTRITIONAL ASSESSMENT;
SPEECH DISORDERS; SWALLOWING DISORDERS.
audiologic assessment Tests to measure hearing
ability and to determine the extent of HEARING LOSS.
An audiologic assessment consists of preliminary
screening and procedures to test specific dimensions
of hearing. A comprehensive audiologic
assessment may take up to an hour to complete
though requires no preparation and involves no
discomfort. Basic screening for hearing ability and
loss should begin in infancy (90 percent of newborns
born in hospitals in the United States are
tested before discharge or at the first newborn wellcare
visit) and continue through life. Health experts
recommend routine screening tests for hearing loss
in adults every five years, more frequently when
there are risk factors, such as noise exposure.
Preliminary Examination
The first step in an audiologic assessment is a preliminary
examination in which the audiologist
examines the structures of the outer and middle
ears with an otoscope. This examination, called an
OTOSCOPY, helps detect structural anomalies as well
as mechanical impediments to sound conduction
(such as compacted CERUMEN in the auditory canal
or an infected or damaged TYMPANIC MEMBRANE).
The preliminary examination also includes a
health history in which the audiologist asks questions
about any existing hearing loss, risk factors
for hearing loss (including noise exposure), medications,
and illnesses such as MEASLES and RUBELLA
(German measles).
Audiometry
An audiologist conducts the procedures of audiometry,
a battery of tests that measure the ability to
discern sounds at different frequencies (pitch) and
intensities (volume). During the audiometric
examination the person sits in a soundproof booth
and the audiologist sits in a control booth.
Common audiometric procedures include
• Pure-tone audiometry, which measures the
range of sound a person can hear. For this procedure,
the audiologist produces tones at certain
frequencies and intensities, and the person
indicates whether he or she hears them. The
audiologist tests each EAR separately.
• Conditioned-play audiometry and visual-reinforcement
audiometry, which adapt conventional
audiometry to children. These methods
use games and visual rewards to elicit responses
to the tones.
• Speech audiometry, which determines the lowest
sound frequency and intensity at which a
person can hear and repeat two-syllable spoken
words (speech-reception threshold), and how
well the person can hear and repeat single-syllable
words spoken at a consistent intensity
(word recognition).
• Pure-tone BONE-conduction audiometry, which
delivers tones through a vibrating device placed
against the bone near the ear. This bypasses the
outer and middle ear when there are conductive
obstructions present (such as OTITIS media
or compacted cerumen in the auditory canal).
The audiologist reports results in decibel (dB) of
threshold (sound intensity) for 500 Hertz (Hz),
1,000 Hz, and 2,000 Hz, the frequencies of everyday
speech and activities. An audiogram summarizes
and presents this information for each ear in
a graphic presentation. Any identified hearing loss
may require additional tests.
Other Hearing Tests
Sometimes health-care providers need further
information to identify the nature and cause of
hearing loss, particularly in infants and young children.
Other tests for refined assessment include
• auditory evoked potentials, in which electrodes
attached to the head measure NERVE transmissions
in response to sound
• auditory brainstem response, an auditory
evoked potential that specifically measures the
response of the eighth cranial nerve (vestibulocochlear
or auditory nerve)