HIS 125 - The Audiologic Evaluation
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Transcript of HIS 125 - The Audiologic Evaluation
THE AUDIOLOGIC EVALUATION
• Critics of clinical audiology assert
that audiometry can be
delegated to a minimally trained
technician, since these tests have
the appearance of being quite
simple to administer.
THE AUDIOLOGIC EVALUATION
• The assumption that audiometry
can be administered by someone
with minimal understanding is a
failure to recognize the complexity
of the principles underlying
accurate audiometric assessment.
THE AUDIOLOGIC EVALUATION
• Pure-tone audiometry has
developed from the basic
principles of the tuning fork tests.
• There are many problems inherent
in the use of tuning forks, and
results can be variable.
THE AUDIOLOGIC EVALUATION
For example: Patients with
longstanding hearing loss have lost
the ability to localize sound and are
apt to provide tuning fork test results
that are inconsistent with their
hearing loss.
THE AUDIOLOGIC EVALUATION
• However, the value of
understanding tuning fork tests
exist in modern audiometry. Every
audiometer used in diagnostic
testing has the capacity to
present tones by air conduction
and bone conduction.
THE AUDIOLOGIC EVALUATION
• The comparison of air and bone
conduction results provides the
basis for determining if middle ear
dysfunction and conductive
hearing loss exists.
THE AUDIOLOGIC EVALUATION
• The two tuning fork tests which are
most commonly used in
audiometry are:
1. The Weber test
2. The Rinne test
THE AUDIOLOGIC EVALUATION
• The Weber test
When the tuning fork is placed at
the mid-line of the forehead and its
tone/sound localizes to the better
ear; this indicates that the opposite
ear has the greatest sensorineural
loss. (It determines the better cochlea)
THE AUDIOLOGIC EVALUATION
• The Rinne test
This compares the loudness of the
tone/sound presented by first bone
then air conduction. A
sensorineural loss is determined if
the air conduction sound is heard
louder or longer than the bone
conduction. (a “positive Rinne”)
THE AUDIOLOGIC EVALUATION
• The Rinne test
A “negative Rinne” result reveals
the presence of a conductive
hearing loss.
THE AUDIOLOGIC EVALUATION
• Finding a THRESHOLD is defined as
the minimum effective sound
pressure that is capable of evoking an auditory sensation
which the patient/client will
respond to fifty percent of the time.
THE AUDIOLOGIC EVALUATION
• The pure tone audiogram is obtained by establishing air-
conduction and bone-conduction
pure-tone thresholds at several
frequencies especially 500Hz,
1000Hz, 2000Hz, 3000Hz, 4000Hz.
THE AUDIOLOGIC EVALUATION
• During air-conduction testing, the
entire auditory system is under
examination.
• Air conduction thresholds are
affected by influences from the
pinna, external and middle ear,
and cochlea.
THE AUDIOLOGIC EVALUATION
• During bone –conduction testing
the middle ear is bypassed and
the result represents an estimation
of cochlear function of the ear.
THE AUDIOLOGIC EVALUATION
• Bone Conduction Testing
The major problem, unique to the measurement of bone-conduction,
Is the lack of effective acoustic separation of the two cochlea.
Bone conduction activates both cochlea simultaneously and nearly equally.
THE AUDIOLOGIC EVALUATION
• Bone Conduction Testing
Weber test results can provide information as to the first ear to test. Always perform bone-conduction on the ear which the Weber test lateralizes to.
Note: There is no need to mask when no air-bone gap is revealed.
THE AUDIOLOGIC EVALUATION
• NOTE
• With today’s digital hearing
instruments, it is critical to also
measure the half octaves
displayed on the audiometer.
• Half octaves normally displayed
are 750Hz, 1.5K, 3K, 6K.
THE AUDIOLOGIC EVALUATION
• NOTE
• When more that a twenty decibel
difference is found between
octaves (500Hz, 1000Hz, 2000Hz,
4000Hz, 8000Hz) it is also
recommended to measure that
half octave.
THE AUDIOLOGIC EVALUATION
• There are three methods used to
by the tester to establish pure
tone thresholds. They are:
1. Ascending method
2. Descending method
3. Bracketing method
THE AUDIOLOGIC EVALUATION
• You have learned the bracketing
method (five decibels up—ten decibels
down). It is a combination of the ascending and descending
method.
• We will continue to use this
method in our audiometric testing
procedure.
THE AUDIOLOGIC EVALUATION
• Assessing Hearing Handicap and Disability
from Pure Tone Audiometry
1. Hearing handicap means the
disadvantage imposed by a hearing loss.
2. Hearing disability is the determination of
compensation for the hearing loss.
Let’s review Northern, chapter four, page #50.
(The hearing loss “label” based upon average hearing
loss level revealed from 500, 1K, 2K average results)
THE AUDIOLOGIC EVALUATION
• Speech audiometry attempts to
measure two clinical quantities.
They are:
1. Speech Recognition Thresholds
(SRT)
2. Word Recognition Ability (WR)
THE AUDIOLOGIC EVALUATION
• SPEECH RECEPTION THRESHOLD
This test uses thirty-six spondee
words (two-syllable words with
equal stress on both syllables).
THE AUDIOLOGIC EVALUATION
• SPEECH RECEPTION THRESHOLD
Audiometers have been calibrated
so that there is close agreement
between the revealed pure tone
average and speech reception
threshold results—within five
decibels of each other.
THE AUDIOLOGIC EVALUATION
• SPEECH RECEPTION THRESHOLD
When there is a large discrepancy
between the PTA and the SRT, this may be one of the first indications
of nonorganic hearing loss.
If the SRT is substantially better than
the PTA other tests may be
warranted.
THE AUDIOLOGIC EVALUATION
• WORD RECOGNITION TESTING
These are administered at suprathreshold levels.
They consist of fifty word lists of words that are phonetically balanced (PB words).
This represents the frequency of occurrence of sounds in everyday English.
THE AUDIOLOGIC EVALUATION
• WORD RECOGNITION TESTING
The variabilities introduced by live-
voice speech testing make that
approach unacceptable for diagnostic
testing.
The use of recorded speech stimuli
ensures that exactly the same stimulus
is presented on test-retest conditions.
THE AUDIOLOGIC EVALUATION
• WORD RECOGNITION TESTING
Most WR word lists are administered
at thirty, forty or fifty sensation levels
(above threshold average)
When PB max tests are not used,
most WR word lists are presented at
the patient/client’s most
comfortable listening level (MCL).
THE AUDIOLOGIC EVALUATION
• WORD RECOGNITION TESTING
PB max tests are used in diagnostic
evaluations to determine if a retro-
cochlear lesion may be present.
When the signal/loudness is
increased, the WR score will
become worse.
THE AUDIOLOGIC EVALUATION
• WORD RECOGNITION TESTING
Also, when WR scores are grossly
poorer relative to the revealed
thresholds--such as a forty decibel
PTA hearing loss with WR scores less
than twenty-five percent; a retro-
cochlear problem may exist.
THE AUDIOLOGIC EVALUATION
• WORD RECOGNITION TESTING
Generally, those with conductive
loss have excellent WR scores.
Those with cochlear hearing loss
have poorer WR scores which will
be also be consistent with a greater
degree of hearing loss.
THE AUDIOLOGIC EVALUATION
• WORD RECOGNITION TESTING
When unusually poor WR results are
revealed relative to threshold
results, a neural lesion may be
present.
THE AUDIOLOGIC EVALUATION
Routine audiometric tests do not
provide information about factors
affecting the central
hearing/auditory pathways.
Speech-in-noise tests are much
more revealing for identifying
Central Processing Disorders.