Impedance (Z) vs. Admittance (Y) Resistance(R) Mass Reactance(Xm) Stiffness Reactance(Xs) Z = (R 2 + X t 2 ) 1/2 Conductance(G) Mass Susceptance(Bm) Stiffness Susceptance(Bs) Y = (G 2 + B t 2 ) 1/2

Mass and Stiffness Reactance Resonant Freq.

Mass and Stiffness Susceptance Resonant Freq.

RESISTANCE AT THE EARDRUM

Reactance at the Eardrum

Tympanogram: A plot of middle ear admittance as a function of ear canal pressure Pressure is swept from +200 to -200 or -400 dPa Should see peak at point where pressures are equal

Static Admittance 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

Gradient = hp/ht

Tympanogram types: A: peak between +100 and -200 dPa: normal C: peak beyond -200 dPa: neg pressure B: no peak flat tymp: effusion A s : peak but shallow: stiff: otosclerosis A d : peak off scale: floppy: dysarticulation

Tympanogram Types

Physical Volume Test Measure of volume of air enclosed under probe Adults3-10 yrs. Intact TM: 0.9 to to 0.9 TM Perf/Tube: > 2.0 >1.0 Blockage: small volume

The Acoustic Reflex Stapedius contraction measured as change in compliance Reflex arc: – peripheral ear, –VIIIth n. –Cochlear nucleus –Superior Olivary Complexes –Medial Nuclei of VII –VIIth nerves to both middle ears

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. Threshold: how intense sound must be to elicit the reflex? A.R. Decay: 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 admittance can be read ipsilaterally or contralaterally should be between 65 and 90 dB SL.

“The Boxes” Probe (Measured) Ear/ Condition RightLeft ContralateralRight ear Reflex Stimulated Contralaterally Left ear Reflex Stimulated Contralaterally IpsilateralRight ear Reflex Stimulated Ipsilaterally Left ear Reflex Stimulated Ipsilaterally

Vertical RightLeft Contralateral PresentAbsent Ipsilateral PresentAbsent 7 th Nerve

Diagonal RightLeft Contralateral PresentAbsent Ipsilateral AbsentPresent 8 th Nerve

Horizontal RightLeft Contralateral Absent Ipsilateral Present Brainstem

Inverted L RightLeft Contralateral Absent Ipsilateral PresentAbsent Conductive/8 th Impinging on 7 th

Eustachian Tube Function Test: To see how well the Eustachian tube can resolve the pressure differences introduced with the bridge. Note tympanogram peak pressure introduce pressure into canal Have patient swallow water recheck tympanogram peak pressure