1 / 27

Development of Improved Noise Metrics and Auditory Risk Assessment Procedure

Development of Improved Noise Metrics and Auditory Risk Assessment Procedure. June 22, 2009 Won Joon Song and Jay Kim Mechanical Engineering Department University of Cincinnati. Contents. Description of noise metric Correlation study between the noise metric and PTS data

kovit
Télécharger la présentation

Development of Improved Noise Metrics and Auditory Risk Assessment Procedure

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Development of Improved Noise Metrics and Auditory Risk Assessment Procedure June 22, 2009 Won Joon Song and Jay Kim Mechanical Engineering Department University of Cincinnati

  2. Contents • Description of noise metric • Correlation study between the noise metric and PTS data • Methodology to determine spectral NIHL threshold SPL • EARM curve and its implementation strategy to NIHL research

  3. Noise group data • Provided by collaborators in SUNY Plattsburgh • 23 noise groups • 18 noises of 100 dBA overall SPL • Additional 5 noises • 3 noises of 90 dBA overall SPL: G-47, G-48 and G-56 • 2 noises of 95 dBA overall SPL: G-57 and G-58 • Complex or Gaussian noise • 20 complex noises • 3 Gaussian noises: G-61, G-47 and G-57

  4. Noise exposure data • Provided by collaborators in SUNY Plattsburgh • Continuous 5-day exposure to 9-16 chinchilla subjects (23 groups, 275 chinchillas in total) • Obtained at 6 frequency points of 0.5, 1.0, 2.0, 4.0, 8.0 and 16.0 kHz • Auditory evoked potential (AEP) measurement • TTS (dB): right after exposure • PTS (dB): after 30 days of recovery • Mechanical damage • OHC loss (%) • IHC loss (%)

  5. Basic designs of noise metric • 6 basic designs reflecting time-frequency characteristics of the noise • 14 metrics derived from basic designs Type 1: Equivalent SPL Type 2: Kurtosis 1/3 octave pressure time history Type 3: Maximum SPL Type 4: Dynamic SPL Type 5: Modified equivalent SPL Type 6: Normalized weighted exposure time

  6. 1/3 octave pressure time-history: Implementation of AWT Pressure time-history • A special version of analytic wavelet transform developed at UC • Signal analyzer to obtain a set of 1/3 octave time histories from a single time history • Useful tool to study spectral noise-to-hearing loss relationship 1/3 octave pressure time-history

  7. Noise metric calculation procedure Pressure time-history Spectral noise metric 0.5 kHz 1.0 kHz 2.0 kHz 4.0 kHz 8.0 kHz 16.0 kHz T-F decomposition by AWT 1/3 octave time-history @ 6 frequency points

  8. Noise metric description Type 1: Equivalent SPL Type 5: Modified equivalent SPL Time average of 1/3 octave sound pressure Time average of 1/3 octave sound pressure above threshold

  9. Noise metric description Type 2: Spectral kurtosis G-61: Gaussian type Statistical quantity representing impulsiveness of a signal β=2.99 ≈ 3 G-63: Complex type β=79.81

  10. Noise metric description Type 3: Max. SPL Type 4: Dynamic SPL Top 95% value of the 1/3 octave SPL distribution histogram Weight to the dynamic fluctuation of 1/3 octave SPL Type 6: Normalized weighted exposure time Application of ‘3 dB exchange rule’ to each sampling time interval

  11. Box plot of PTS data

  12. Noise vs. frequency correlation Noise correlation: frequency by frequency Noise metric surface Frequency correlation: noise by noise PTS surface (median)

  13. Example of noise metric vs. median PTS: Complex noise (G-63) Spectral kurtosis Median PTS

  14. Example of noise metric vs. median PTS: Gaussian noise (G-61) Spectral kurtosis Median PTS

  15. Correlation study with 18 noises Frequency correlation Noise correlation Correlation scale:

  16. Correlation study with 23 noises Frequency correlation Noise correlation Correlation scale:

  17. NIHL threshold SPL determined by statistical process Scatter plot of Leq-PTS (1.0 kHz) Linear regression line Upper prediction bound C.I. Lower prediction bound Threshold SPL curve 0 dB PTS Lower prediction bound Threshold SPL (1.0 kHz)

  18. NIHL threshold SPL curve construction 4.0 kHz 1.0 kHz 2.0 kHz 8.0 kHz 0.5 kHz 16.0 kHz

  19. Improved noise metric with variable threshold Type 5a: Modified equivalent SPL with variable threshold Time average of 1/3 octave sound pressure time history above frequency-dependent thresholds

  20. Variation of the equivalent sound pressure Time averaging T-F decomposition Conventional Type 1 Type 5 Constant threshold Type 5a Variable threshold

  21. Constant vs. variable threshold Constant threshold Variable threshold

  22. Equal auditory risk metric (EARM) curve construction Scatter plot of Lem-PTS (1.0 kHz) Linear regression line Upper prediction bound C.I. Lower prediction bound EARM curves Lower prediction bound

  23. Interpretation of EARM curves Slow development of PTS Iso-PTS curves (10,20,30,40,50dB) Fast development of PTS NIHL threshold metric curve (0 dB PTS curve) PTS-free zone

  24. Application of EARM curve to NIHL study: Noise reduction level Recommended spectral noise reduction level to protect the auditory system Noise reduction level required at 8.0 kHz NIHL threshold metric curve (0 dB PTS curve) Noise metric curve (G-47) No noise reduction required at 2.0 kHz

  25. Application of EARM curve to NIHL study: PTS prediction PTS at 4kHz (estimated by interpolation) 0 dB PTS at 2.0 kHz Noise metric curve (G-47)

  26. Validity checking of EARM curve prediction Acceptable PTS prediction band Overestimation at 0.5, 8.0, and 16.0 kHz Over-estimated Predicted PTS at 8.0 kHz Properly-estimated Measured PTS at 8.0 kHz Under-estimated

  27. Questions?

More Related