Hearing testing in children
It is never too early to test a child's hearing. The type of procedure used
to test hearing will depend upon the age of the child.
Common types of testing
Soundfield (behavioral) Testing
During soundfield testing, the child sits on the parent's lap. Sounds are
presented to the soundfield via loudspeakers. The audiologist(s) watches the
child as he responds to the sounds. In very young children, the audiologist will
look for responses such as an eyeblink or slight body movement. Older children
are trained to turn toward the sound. When turning toward the sound, the child
then will see a lighted toy as a reward.
Testing under headphones
Headphone testing provides the audiologist
with information regarding the child's ability to hear with each ear. Testing
usually begins by finding the softest level at which the child is able to repeat
words or point to pictures. The child then is taught to respond to the sounds of
various pitches by raising his hand or by performing an act such as dropping a
block into a container. This test is referred to as an audiogram and evaluates
the child's ability to hear certain sound frequencies.
Bone conduction testing
Bone conduction testing evaluates the
function of the inner ear or nerve portion of the ear. A small vibrator is
placed behind the child's ear and he is asked to repeat or identify words or
respond to sounds of different frequencies. The results of this test are
compared to results obtained under headphones or through loudspeakers to help
the audiologist identify the type of hearing loss.
Otoacoustic emissions
Otoacoustic emission testing assesses the
function of the inner ear, specifically the outer hair cells. A small probe is
placed in the child's ear. Sounds are presented to the ear and an emission
("echo") from the ear is measured. The result helps us to determine whether a
child has normal hearing.
Immittance testing
Immittance testing, often referred to as a
tympanometry, provides information regarding eardrum mobility and middle ear
function. A small plastic tip is placed in the child's ear to make an airtight
seal. Changes in air pressure are made and measures are taken. If the child has
ear tubes, this test helps determine if the tubes are in place, open, and
working properly. If the child does not have tubes, this test helps determine if
there are any signs of fluid or other problems in the middle ear. Reflex action
of the ear (acoustic reflexes) also is measured with immittance testing.
Auditory Brainstem Response (ABR) Testing
What is the ABR?
The ABR is a test that provides information regarding the softest level of
sound that a person can hear. During the test, several electrodes are taped onto
the child's head and a small earphone is placed into each ear. These electrodes
are used to monitor brainwave activity as the child listens to sounds at
different levels of loudness.
The brainwave patterns of the ABR are evaluated to determine the softest
level of sound each ear can hear. If there is a hearing loss, the ABR helps to
determine the type and severity of the problem.
Who Should Have an ABR?
The ABR is most commonly recommended for
infants or very young children when a hearing loss is suspected. It can also be
used to evaluate older children who will not cooperate during other types of
hearing tests. The ABR is usually not necessary in healthy children over three
years of age, if the child will wear headphones and cooperate during a
behavioral hearing test.
The ABR often is performed as part of a complete test battery, which includes
behavioral testing and tympanometry and otoacoustic emissions. It is important
that a series of tests be performed to more accurately determine the presence,
degree and type of hearing loss.