Otoacoustic Emissions Low-level sounds produced by the
cochlea and recordable in the external ear canal.
Spontaneous Click-evoked Distortion Product Stimulus Frequency
History First described by Kemp (1977 &
1978), But predicted by Gold (1948!) Supported by almost simultaneous
discovery of OHC motility Movement into Clinical Use:
Screening for hearing loss Role in Audiologic Battery
Anatomy and Physiology
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:
“Reverse Traveling Wave” is debated
Through Middle Ear: Filtering and attenuation
Into ear canal Note: requirement of healthy middle ear and clear outer ear.
Neonatal Hearing Screening
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
Audiologic Battery
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
Emission Frequency
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OAE as Measure of Cochlear Health
Tone Decay:
Loss of audibility for a tone that is on continuously.
Greater decay is indicative of retrocochlear problem.
There are different methods:
Some Tone Decay Tests
Carhart: begin at 0 SL, up in 5 dB steps until tone is heard for a full minute
Olson-Noffsinger: begin at 20 SL, up until heard for full minute.
Tone Decay Results:
Type I: no decay: norm, conduct or cochlear
Type II: heard for longer times as level is increased: cochlear
Type III: No growth with increasing level: retrocochlear
TONE DECAY SUCCESS?
Sensitivity = 75% Specificity = 91%
Auditory Brainstem Response:
Response within 10 ms of stimulus waves labeled with Roman
numerals Peaks I, III, and V most useful Latencies are the key measure Disorders will produce delays
ABR SUCCESS?
Sensitivity = 97% Specificity = 88%
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