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Kevin CP Yuen Institute of Human Communicative Research &

Comparative performance of an adaptive directional microphone and a multi-channel noise reduction system , in a digital hearing instrument. Kevin CP Yuen Institute of Human Communicative Research & Division of Otolaryngology, Department of Surgery, The Chinese University of Hong Kong

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Kevin CP Yuen Institute of Human Communicative Research &

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  1. Comparative performance of an adaptive directional microphone and a multi-channel noise reductionsystem, in a digital hearing instrument Kevin CP Yuen Institute of Human Communicative Research & Division of Otolaryngology, Department of Surgery, The Chinese University of Hong Kong Anna CS Kam Phonak Hong Kong Hearing Centre Polly SH Lau Division of Speech and Hearing Sciences, The University of Hong Kong 8 Oct 2005

  2. Objectives • Compare the speech recognition in noise performance among • Multi-channel noise reduction system (medium) (FNC), • Adaptive directional microphone (DAZ), & • FNC + DAZ • Compare the objective and subjective performance between • NAL-NL1 in Perseo, & • Digital Perception Processing (DPP) in Perseo

  3. Multi-channel noise reduction system -Fine noise canceller, FNC (Medium) • Frequency-dependent gain reduction • SNR-dependent gain reduction Courtesy of Phonak

  4. Adaptive directional microphone (DAZ) • Polar patterns are switched adaptively in response to the direction of noise Courtesy of Phonak

  5. NAL-NL1 & DPP • NAL-NL1, National Acoustics Laboratory – Non-linear 1 (Dillion, 1999) • Provides gain-frequency response that maximizes speech intelligibility for any input level of speech, • while keeping overall loudness at a level no greater than that perceived by a normal hearing person, or at a lower level if it provides greater speech intelligibility. • DPP, Digital Perception Processing • Incorporates a psychoacoustic loudness mode of normal and impaired cochlea function (Moore et al, 2003) • Calculates excitation patterns and specific loudness patterns evoked in a normal and impaired cochlear, from the incoming signal, and adjusts gain required to match the loudness patterns of impaired cochlea to those of normal cochlea • Aims at restoring loudness perception to ‘normal’

  6. Research Design Group 1 (5 subjects) OWN hearing aid → Perseo DPP →Perseo NAL-NL1 Group 2 (4 subjects) OWN hearing aid → Perseo NAL-NL1 →Perseo DPP 1 week 1 week Perseo DPP =Digital Perception Processing target Perseo NAL-NL1= NAL-NL1 target

  7. Assessment tools • DPP vs NAL-NL1 / FNC+DAZ vs DAZ vs FNC • Cantonese Hearing-in-Noise Test (CHINT) • (Wong & Soli, 2005) • Chinese translated version of Abbreviated Profile of Hearing Aid Benefit (APHAB) • (Cox & Alexander, 1995) • DPP vs NAL-NL1 • Sound quality paired comparison judgment

  8. Subjects • Nine post-lingually deafened adults (39-79 yrs) • Sensorineural hearing loss • Native Cantonese-speaking • Hearing aid experience > 6 months Average unaided air-conduction threshold of the test ear (+/- 1 SD)

  9. Speech recognition in noise results • Separately for • Signal_Front/ Noise_Front & • Signal_Front/ Noise_Side • Run Two-way repeated measures ANOVA for • Noise suppression (FNC+DAZ vs DAZ vs FNC) • Prescription (DPP vs NAL-NL1) & Post-hoc Tukey HSD test

  10. Results Noise suppression options FNC+DAZ vs DAZ vs FNC

  11. FNC+DAZ vs DAZ vs FNCSignal_Front / Noise_Front

  12. FNC+DAZ vs DAZ vs FNCSignal_Front / Noise_Side

  13. Results Prescriptions DPP vs NAL-NL1

  14. DPP vs NAL-NL1Signal_Front / Noise_Front

  15. DPP vs NAL-NL1Signal_Front / Noise_Side

  16. APHAB DPP vs NAL-NL1 Wilcoxon Signed-Ranks Test

  17. Sound quality paired comparison judgmentDPP vs NAL-NL1

  18. Sound quality paired comparison judgmentDPP vs NAL-NL1

  19. Sound quality paired comparison judgmentDPP vs NAL-NL1 Wilcoxon Signed-Ranks Test, p =.26 D N NAL DPP

  20. Real ear SPL difference DPP minus NAL-NL1 DPP Difference, dB DPP DPP DPP

  21. Conclusion • Speech recognition in noise • With signal and noise from the front, • DPP better than NAL-NL1 in 1 subject • FNC, DAZ and FNC+DAZ were not different • With signal from the front, noise from the side • DPP better than NAL-NL1 in 4 subjects • DAZ better than FNC in 8 subjects • FNC+DAZ better than FNC in 6 subjects • Whenever there was a difference, DPP was better than NAL-NL1 • Adaptive Directional Mic better than Multiband noise reduction system, only for signal_front/noise_side but not for signal_front/noise_front • best speech recognition, measured AI-weighted directional pattern for signal_front/noise_side (Ricketts et al, 2002)

  22. Conclusion • APHAB • NAL-NL1 > DPP (Adversiveness) • DPP> NAL-NL1 (Reverberation) • Sound quality paired comparison judgment • 5/9 subjects had more preferences towards DPP than NAL-NL1 • 3/9 subjects had more preference towards NAL-NL1 than DPP

  23. NAL-NL1English does not maximize speech intelligibility for Cantonese ? • Band importance function • English sentence – peak at 2000Hz (Eisenberg et al, 1998) • Cantonese sentence – peak at 800-1600Hz (Chua, 2004) • Band importance function -> derive SII -> derive NAL-NL1 Chua, 2004

  24. Kevin Yuen Division of Otorhinolaryngology, Department of Surgery The Chinese University of Hong Kong Email: kevinyuen@surgery.cuhk.edu.hk

  25. 2cc coupler gain response of the three hearing aid settings (front microphone @ 0 degree azimuth)

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