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Audiological Evaluation >> Immittance Measurements
Immittance Measurements
A common cause of hearing loss in both
children and adults is middle ear dysfunction. Problems such as middle
ear infections, perforated eardrums, or problems with the small bones
in the middle ear can result in hearing loss. Immittance
Measurements are used to diagnose problems in the middle ear. To obtain a tympanogram, a small
earphone is placed in the ear canal and eardrum movement is measured in
response to air pressure changes. The acoustic reflex test checks the function of a small muscle
in the middle ear
Tympanometry is an examination used to test the condition of the middle
ear and mobility of the tympanic membrane (eardrum)
and the conduction bones by creating variations of air
pressure in the ear canal. Tympanometry
is an objective test of middle-ear function. It is not a hearing
test, but rather a measure of energy transmission through
the middle ear. The test should not be used to assess the sensitivity
of hearing and the results of this test should always be viewed in
conjunction with other hearing tests including the pure tone audiometry
if available.
Acoustic Reflex Testing consists of subjecting the
ear to a loud sound (pure tone or noise) and determining if it causes
middle ear muscle (Stapedius muscle)
contraction. The muscle contraction is elicited in the
presence of loud sounds and serves as a protective mechanism for the
ear. Acoustic
reflex testing is mainly useful as a crude but non-subjective method of
evaluating hearing; it provides additional information
about the presence of a hearing impairment and assists in determining
the type of impairment.
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