Objective Tests of the Auditory System

SPA 4302

Summer 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 Potentials

Recording: Comes From:

Electrocochleography Cochlea, VIIIth nerve

Auditory ________ Response

__________________

Middle Latency Response Thalamus & _______ cortex

Auditory _____ Response Auditory Cortices

__________ Hippocampus area

ABR MEASURES

Time (ms)

Am

plit

ude

(μV

)

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