Mid Term Flashcards
Impedance (Za) = resistance (Ra) + reactance
Impedance (Za) = resistance (Ra) + reactance
Admittance (Ya) = Conductance (Ga) + Susceptance (j or -jBa)
Admittance (Ya) = Conductance (Ga) + Susceptance (j or -jBa)
Impedance
resistance of flow of sound energy
what affects impedance?
acoustic resistance, compliant acoustic reactance, mass acoustic reactance
Compliance susceptance
ease of flow through a system
what freq. is compliant susceptance greatest?
low freq.
Mass Susceptance
ease of sound flow through a mass or inertial elements
what freq. is mass susceptance greatest
high freq.
Stiffness contributions to ME function
TM, round window, ossicular ligaments, ME muscles, air within EAC & ME
Mass contributions to ME function
ossicles, air movement in ME, frictional properties inherent to air movement within the system
Resonance
compliant acoustic susceptance and mass acoustic susceptance are equal and cancel each other out
Components of tympanometer
probe, pneumatic system (changes air pressure), acoustic immittance measurement system (converting difference between driver and mic), acoustic reflex activator system (ipsi & contra)
Type 1 Tympanometer
manual & auto, ipsi & contra, noise & pure-tone
Type 2 tympanometer
manual & auto, ipsi & contra, pure-tone, what we use
Type 3 tympanometer
static immittance & tymps, acoustic reflex at specified levels, used for screenings
Type 4 tympanometer
can separately do static immittance, tymps, or reflexes
What systems need calibration?
probe signal, acoustic immittance measurement system, pneumatic system, acoustic reflex activating system
What do we look at when calibrating probe signal?
output level, freq. accuracy, harmonic distortion
What do we look at when calibrating acoustic immittance measurement system?
calibration cavities equals admittance magnitude–> 0.5 cc=0.5 mmhos, 2.0cc=2.0 mmhos, 5.0cc=5.0mmhos
What do we look at when calibrating pneumatic system?
pressure changes: type 1 & 2= +200 and -600 daPa, Type 3= +100 and -300 daPa
What do we look at when calibrating acoustic reflex activating system?
freq. accuracy, output levels, attenuator linearity, harmonic distortion, temporal characteristics of instrument (initial latency, rise time, terminal latency, fall time, drift)
What due admittance measures tell us?
about ME function, Eustachian tube function, and indicates ME effusion, patency of PE tubes, and TM perforations
What do reflex measures tell us?
function of ME pathway (stapedius muscle), sensory pathway, neural pathway, and motor pathway
Parts of tymp tubes
manometer, mic, speaker
What do LF (226/220 Hz) tymps tell us?
assess stiffness of ME (effusion affects stiffness)
Importance of ECV
provides insight to etiology of flat tymp.
Norms for Tymps ECV–> Birth to 4 months
0.3 cc
Abnormal Tymps ECV–> Birth to 4 months
greater than 1.0 cc
Norms for Tymps ECV–> 2.8 to 5.8 years
0.4 to 0.9 cc
Abnormal tymp ECV–> 2.8 to 5.8 years
greater than 1.0 cc
Norms for tymp ECV–> 6 weeks to 6.7 years
0.3 to 0.9 cc
Abnormal tymp ECV–> 6 weeks to 6.7 years
1.0 to 5.5 cc with PE tubes