objective tests of the auditory system
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Objective Tests of the Auditory System. SPA 4302 Summer 2007. ______________(R) Mass Reactance(Xm) Stiffness Reactance(Xs) Z = ( R 2 + X t 2 ) 1/2. _____________(G) Mass Susceptance(Bm) Stiffness Susceptance(Bs) Y = (G 2 + B t 2 ) 1/2. Impedance (Z) vs. Admittance (Y). - PowerPoint PPT PresentationTRANSCRIPT
Objective Tests of the Auditory System
SPA 4302Summer 2007
Impedance (Z) vs. Admittance (Y)
______________(R)Mass Reactance(Xm)
Stiffness Reactance(Xs)
Z = (R2 + Xt2)1/2
_____________(G)Mass Susceptance(Bm) Stiffness
Susceptance(Bs)
Y = (G2 + Bt2)1/2
Tympanogram:
A plot of middle ear admittance as a function of __________________
Pressure is swept from +200 to -200 or -400 dPa
Should see peak at point where pressures are ______________
Tympanogram types:
A: peak between +100 and -200 dPa: normal
C: peak beyond -200 dPa: neg pressure B: no peak flat tymp: ____________ As: peak but shallow: stiff: _____________ Ad: peak off scale: floppy: _____________
Tympanogram Types
Static Admittance A measure of the height of tympanogram peak
Adults 3-10 yrsA 0.30 to 1.70 0.25 to 1.05As < 0.30 < 0.2Ad >1.70 > 1.05
(All values are in ml of equivalent volume)
The Acoustic Reflex Stapedius contraction measured as
change in ___________ Reflex arc:
peripheral ear, ___________________ Cochlear nucleus___________________Medial Nuclei of VII______________________
R L
SOC
CN
8th
IE
ME
OE
SOC
CN
8th
IE
ME
OE
7th CN 7th CN
MN 7MN 7
Clinical Tests using Acoustic Reflexes:
A.R. ___________: how intense sound must be to elicit the reflex?
A.R. __________: Is the degree of a contraction maintained throughout a 10 second stimulus?
AR Threshold:
to pure-tones, 0.5, 1, 2, 4 kHz = lowest level at which change in
__________ can be read ipsilaterally or contralaterally should be between ___ and ___ dB SL.
Otoacoustic Emissions (OAE)
Low-level sounds produced by the _______ and recordable in the external ear canal.
Spontaneous Click-evoked _________ Product Stimulus __________
Recording OAEs
Spectrum of Sound in Ear Canal
OAE as Measure of Cochlear Health
Auditory Evoked PotentialsRecording: Comes From:
Electrocochleography Cochlea, VIIIth nerve
Auditory ________ Response
__________________
Middle Latency Response Thalamus & _______ cortex
Auditory _____ Response Auditory Cortices
__________ Hippocampus area
ABR MEASURES
Time (ms)
Am
plitu
de (μ
V)
Wave V Latency
I-V IPL
I-III III-V
I IIIII
IVV
Amp V
Conductive Loss: Curve shifted to higher levels by amount of conductive loss
Severe Cochlear Losses