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 dimen-
sions 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 new-
borns born in hospitals in the United States are
tested before discharge or at the first newborn well-
care 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 pre-
liminary 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 CERUMENin the auditory canal
or an infected or damaged TYMPANIC MEMBRANE).
The preliminary examination also includes a
health history in which the audiologist asks ques-
tions about any existing hearing loss, risk factors
for hearing loss (including noise exposure), med-
ications, and illnesses such as MEASLESand RUBELLA
(German measles).
Audiometry
An audiologist conducts the procedures of audiom-
etry, 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 pro-
cedure, the audiologist produces tones at cer-
tain frequencies and intensities, and the person
indicates whether he or she hears them. The
audiologist tests each EARseparately. - Conditioned-play audiometry and visual-rein-
forcement audiometry, which adapt conven-
tional audiometry to children. These methods
use games and visual rewards to elicit responses
to the tones. - Speech audiometry, which determines the low-
est 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-syl-
lable 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 conduc-
tive obstructions present (such as OTITISmedia
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 every-
day speech and activities. An audiogram summa-
rizes 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 chil-
dren. Other tests for refined assessment include- auditory evoked potentials, in which electrodes
attached to the head measure NERVEtransmis-
sions in response to sound - auditory brainstem response, an auditory
evoked potential that specifically measures the
response of the eighth cranial nerve (vestibulo-
cochlear or auditory nerve)
audiologic assessment 9