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Signal Processing Seminar: Pole-zero Characterization of Middle Ear Acoustic Reflectance Data

Event Type
Signal Processing Seminar
4269 Beckman Institute
Dec 5, 2012   4:00 pm  
Sarah Robinson, University of Illinois

Middle ear acoustic reflectance (AR) measurements have valuable clinical applications. AR is measured using a foam-tipped probe sealed in the ear canal, containing a microphone and sound source (i.e. MEPA3 system, Mimosa Acoustics). From the complex pressure response to a broadband stimulus, the acoustic impedance and reflectance of the middle ear can be calculated as functions of frequency.  A sizeable pool of normal and pathological AR data, collected by various researchers, indicates that many pathological ears have an AR that systematically differs from normative data.  Assessment of such data typically relies on consideration of the magnitude AR, or separate consideration of AR magnitude and phase. By fitting poles and zeros to AR data, we have achieved a concise and accurate parameterization of the complex data (<3% average RMS relative error using 12 poles, for MEPA3 data measured from 0.2 to 6 kHz). It was found that the contribution of the ear canal may be approximated as the lossless all-pass component of the factored reflectance fit.  It was also found that individual CAR magnitude variations for normal middle ears in the 1 to 4 kHz range give rise to closely-placed pole-zero pairs, and that the locations of the poles and zeros in the s-plane differ between normal and pathological middle ears. Pole-zero fitting allows for concise characterization of individual CAR measurements, providing a foundation for modeling the individual and pathological variation of middle ears.

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