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Immittance Testing
Question | Answer |
---|---|
Acoustic Immittance | The ease of (or opposition to) flow of sound through a system. |
What is "immittance" composed of? | Acoustic Impedance and acoustic admittance |
Acoustic Impedance | The opposition to the transfer of acoustic energy through the auditory system. Measured in acoustic ohms (Za). How much sound bounces back - the harder the surface the more sound bounces back (not a lot of sound going through). |
Acoustic Admittance | The ease of energy flow or transfer of acoustic energy through the auditory system. Reciprocal of impedance. Measured in mmhos (Ya). |
What are the components for dissipation of energy? | Acoustic Resistance (Impedance) and Acoustic Conductance (Admittance) |
What are the components for storage of energy? | Acoustic Reactance (Impedance) and Acoustic Susceptance (Admittance) |
What type of system is dominant at low frequencies? High frequencies? | At low frequencies the system is stiffness dominant. At high frequencies the system is mass dominant. |
What are the four basic immittance measures? | Tympanometry (measure immittance as a function of air pressure), acoustic (stapedial) reflex measures (measurement of immittance as a function of loud sounds), eustachian tube function (measurement of patency of eustachian tube), fistula (vertigo testing) |
What are the norms for compliance in infants (over 6 months old)? For children aged 1-8 yrs old? | >.20 mmhos for infants and >.30 mmhos for children ages 1-8 yrs old |
What are the equivalent ear canal volumes for neonates? Children? Adults? Patent tubes in children? | 1) Neonates: usually < .50cc 2) Children: .30-1.0 (0.9) cc 3) Adults: 0.65 (.63) - 1.75 (1.46) cc 4) Patent tubes in children: 1.0 - 5.5 cc |
What is the pump speed of the tympanometer on screening mode? Diagnostic mode? | Screening - 200 daPa/second and Diagnostic - 50 daPa/second |
What is the ASHA screening guideline for TW for "abnormal" results? AAA screening guideline? | ASHA > 200 daPa and AAA > 250 daPa |
What is considered "abnormal" diagnostically for TW? | TW > 275 daPa |
According to ASHA, what is the referral criteria for tympanometry? | 1) drainage, abnormality of ear canal, TM, or ear that was previously undetected 2) Volume > 1.0 cc and flat tympanogram (if not already under physician care |
You would repeat tympanometric screening in 6-8 weeks if.... | 1) Compliance < .30 mmho (children) or < .20 mmho (infants) 2) Width > 200 daPa (children) or >235 daPa (infants) 3) If second screening fails, refer to physician |
What are the biological reasons for acoustic reflexes? | 1) Intensity control 2) Static control/position 3) Low frequency regulation |
What are the clinical purposes of acoustic reflex testing? | 1) Det. site of dysfunction via comparing ipsi and contra-lateral responses 2) Det. hearing sensitivity and/or site of dysfunction via acoustic reflex threshold measures 3) Det. status of ME, cochlea, VII and VII nerve, and brainstem |