Download Otoacoustic Emissions

Otoacoustic Emissions
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Low-level sounds produced by the
cochlea and recordable in the external
ear canal.
Spontaneous
Click-evoked
Distortion Product
Stimulus Frequency
History
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First described by Kemp (1977 & 1978),
But predicted by Gold (1948!)
Supported by almost simultaneous
discovery of OHC motility
Movement into Clinical Use:
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Screening for hearing loss
Role in Audiologic Battery
Anatomy and Physiology
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Generators = Outer Hair Cells
“Pre-neural”
Low-level event//High level stimuli
produce their own distortions
Reduction/Loss of emission in NITTS
SOAEs correlated to number of rows of
OHCs
Energy Path:
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“Reverse Traveling Wave” is debated
Through Middle Ear: Filtering and
attenuation
Into ear canal
Note: requirement of healthy middle
ear and clear outer ear.
Clinical Utility -- Neonatal
Hearing Screening
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Transient and Distortion-Product OAEs
Rationale: quick, relatively inexpensive,
possibly catching losses in a broader
frequency range than ABR
NIH (1994) recommended two-stage
protocol combining OAEs and ABR
Clinical Utility-- in the Audiologic
Battery
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Assessment of cochlear health in site-of
lesion testing
Objective info on peripheral auditory
functioning
Correlation to audiogram
Assessment of Auditory Efferents
through Contralateral Suppression
Recording OAEs
Spectrum of Sound in Ear Canal
Stimulus Tones
Background Noise
Emission
Frequency
OAE as Measure of Cochlear
Health
Caveats--Remember:
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there is more to “Hearing” than a
healthy cochlea
what lies between your equipment and
the source?
high level stimuli evoke response from
inanimate cavities (e.g. in cadavers)