Objective Tests of the Auditory System SPA 4302 Summer 2007

Impedance (Z) vs. Admittance (Y) ______________(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

Tympanogram: A plot of middle ear admittance as a function of __________________ Pressure is swept from +200 to -200 or 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: ____________ A s : peak but shallow: stiff: _____________ A d : peak off scale: floppy: _____________

Tympanogram Types

Static Admittance A measure of the height of tympanogram peak Adults 3-10 yrs A 0.30 to to 1.05 As < 0.30 < 0.2 Ad >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 8 th IE ME OE SOC CN 8 th IE ME OE 7 th CN MN 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 Potentials Recording:Comes From: ElectrocochleographyCochlea, VIIIth nerve Auditory ________ Response __________________ Middle Latency ResponseThalamus & _______ cortex Auditory _____ ResponseAuditory Cortices __________Hippocampus area

ABR MEASURES Time (ms) Amplitude (μV) Wave V Latency I-V IPL I-III III-V I II III IV V Amp V

Conductive Loss: Curve shifted to higher levels by amount of conductive loss

Severe Cochlear Losses