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Introduction to Auditory Simulation Methods Applicable to NIHL Study

Introduction to Auditory Simulation Methods Applicable to NIHL Study. June 22, 2009 Won Joon Song and Jay Kim Mechanical Engineering Department University of Cincinnati. Contents. Network model Transfer function model Applicability of simulation models to NIHL study. Skull.

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Introduction to Auditory Simulation Methods Applicable to NIHL Study

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  1. Introduction to Auditory Simulation Methods Applicable to NIHL Study June 22, 2009 Won Joon Song and Jay Kim Mechanical Engineering Department University of Cincinnati

  2. Contents • Network model • Transfer function model • Applicability of simulation models to NIHL study

  3. Skull Auditory pathways in conventional network models ME air space Generally replaced by cochlear input impedance B.C Bone conduction Mechanical transmission Modeled as independent block Acoustic transmission

  4. Schematic of network ear model

  5. Classicalmiddle ear network model Network sub-structures and parameter values are different, but three-impedance-block concept is common in typical network models. • Tympanic membrane & ossicular chain up to I-S joint • Two-port network of conductive pathway • Stapes complex & cochlear input impedance • Impedance B.C. for ME transmission • Middle ear cavity • Decoupled from mechanical pathway

  6. Available outputs from network model Steady state response: HFT(ω) HDP(ω) HP(ω) HUP(ω) HC(x, ω) Time-domain response: PFF(t) PTM(t) UST(t) PC0(t) dBM(x, t) dST(t) Source External Ear Inner Ear Middle Ear ZME ZC0 ZEE

  7. Limitations of middle ear network models • Complex vibrational mode of the tympanic membrane: single-piston or mechanically coupled two-piston modeling • Rocking motion of the stapes footplate: translational motion only • Variable middle ear transformer ratio • Moving axis of rotation • Flexible ossicular joints: rigid M-I joint assumed • Effective area change in TM and stapes footplate • Nonlinear acoustic reflex characteristics • Time-frequency dependent • Threshold, adaptation, and saturation features • Nonlinear mechanical properties of the annular ligament • Highly complicated cochlear input impedance: over-simplified

  8. Network model simulation example: Simulink version of AHAAH • Acoustic wave • TM input pressure • Stapes displacement Nonlinear model block

  9. Network model simulation example: Human cochlear model in AHAAH Network model (Simulink) Cochlear model (Matlab) HC (x,ω) IFFT dST (ω) dBM (x,ω) dBM (x,t) dST (t) FFT BM characteristicfreq.-time BM location-time

  10. Transfer function method: An alternative to network model • Free from modeling artifacts • Wider valid frequency range • Responses only up to stapes • Linear concept Source External Ear Middle Ear Inner Ear Replaced by measured TFs

  11. Transfer function method: Stapes response calculation TF from free-field sound pressure to stapes volume velocity FFT Stapes response in frequency domain IFFT Stapes response in time domain

  12. Available transfer functions Human Chinchilla Guinea pig Cat HFT Shaw, E. A. G. (1974)** Mehrgardt & Mellert (1977) Bismarck & Pfeiffer (1967)* Murphy & Davis (1998) Sinyor & Laszlo (1973)** Wiener et al. (1965)** HUP Kringlebotn & Gundersen (1985) Ruggero et al. (1990) Nuttall (1974) Guinan & Peake (1967) * Azimuth: 0° ** Phase data not available

  13. Currently available data: Magnitude of HFT Chinchilla: Bismarck & Pfeiffer (1967) Chinchilla: Murphy & Davis (1998) Cat: Wiener et al. (1965) Guinea pig: Sinyor & Laszlo (1973) Human: Shaw (1974) Human: Mehrgardt & Mellert (1977)

  14. Currently available data: Phase of HFT Chinchilla: Murphy & Davis (1998) Human: Mehrgardt & Mellert (1977)

  15. Currently available data: Magnitude of HUP Chinchilla: Ruggero et al. (1990) Cat: Guinan & Peake (1967) Guinea pig: Nuttall (1974) Human: Kringlebotn & Gundersen (1985); Rosowski (1994) Human: Kringlebotn & Gundersen (1985); Rosowski (1991)

  16. Currently available data: Phase of HUP Chinchilla: Ruggero et al. (1990) Cat: Guinan & Peake (1967) Guinea pig: Nuttall (1974) Human: Kringlebotn & Gundersen (1985); Rosowski (1994) Human: Kringlebotn & Gundersen (1985); Rosowski (1991)

  17. Transfer function reconstruction • Target • Spectral range up to 25 kHz • Species: human and chinchilla (due to insufficient data for guinea pig and cat) • Within measured frequency range • Approximated by spline function passing through the measured data points • Out of measured frequency range • Curve-fitting of measured data subset • Extrapolation of the fitted curve

  18. Transfer function reconstruction example: HFT Human: Mehrgardt & Mellert (1977) Gauss2 (0.96, f<1 kHz) Poly1 (0.91, f> 8 kHz) Chinchilla: Murphy & Davis (1998) Sin4 (0.97, f<1 kHz) Fourier6 (0.92, f>15 kHz)

  19. Transfer function reconstruction example: HUP Human: Kringlebotn & Gundersen (1985); Rosowski (1994) Exp2 (0.99, f>1 kHz) Poly7 (0.99, f<1 kHz) Chinchilla: Ruggero et al. (1990) Power2 (0.84, f>1 kHz) Poly5 (0.99, f<1 kHz)

  20. Reconstructed transfer function Chinchilla Human

  21. TF model simulation example:Stapes response to complex noise Human Complex (G-44) Chinchilla

  22. TF model simulation example:Stapes response to impulsive noise Human ±20μm Test impulse Chinchilla

  23. Application to NIHL study: Auditory response metric Network / TF model Velocity-based metric Displacement-based metric EARM curve NIHL study

  24. Questions?

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