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Will technological advances improve the outcome?

Will technological advances improve the outcome?. Ruth Bentler University of iowa. What is new ?. Choices re feedback control Options re directional microphones Digital noise reduction. Directional microphones. Polar Response Pattern.

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Will technological advances improve the outcome?

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  1. Will technological advances improve the outcome? Ruth Bentler University of iowa

  2. What is new? • Choices re feedback control • Options re directional microphones • Digital noise reduction

  3. Directional microphones

  4. Polar Response Pattern Free field characteristics of different types of microphones (Knowles TB 21) Omnidirectional Cardioid Hypercardioid Supercardioid

  5. Quick Tutorial • Ways to build directivity into a hearing aid case: • Single mic with two ports • Two omni mics • Combination of a & b (DMic, eg) • Three mics (Siemens Triano) • Mic array (Etymotic Link-It, e.g.)

  6. Quick tutorial cont • Ways to implement directionality in the hearing aid case: • Fixed polar pattern • Program different polar patterns in different memories • Automatic directional mode • Dynamic/Adaptive directional mode

  7. 90 1 120 60 0.8 0.6 150 30 0.4 0.2 180 0 210 330 240 300 270 Adaptive Directionality

  8. 90 1 120 60 0.8 0.6 150 30 0.4 0.2 180 0 210 330 240 300 270 Adaptive Directionality

  9. 90 1 120 60 0.8 0.6 150 30 0.4 0.2 180 0 210 330 240 300 270 Adaptive Directionality

  10. 90 1 120 60 0.8 0.6 150 30 0.4 0.2 180 0 210 330 240 300 270 Adaptive Directionality

  11. 90 1 120 60 0.8 0.6 150 30 0.4 0.2 180 0 210 330 240 300 270 Adaptive Directionality

  12. 90 1 120 60 0.8 0.6 150 30 0.4 0.2 180 0 210 330 240 300 270 Adaptive Directionality

  13. 90 1 120 60 0.8 0.6 150 30 0.4 0.2 180 0 210 330 240 300 270 Adaptive Directionality

  14. 90 1 120 60 0.8 0.6 150 30 0.4 0.2 180 0 210 330 240 300 270 Adaptive Directionality

  15. In a diffuse field…. 90 1 120 60 0.5 150 30 180 0 210 330 240 300 270

  16. Ricketts & others (1999-02) • Two mics capable of providing same advantage to user as one mic design; • Digital implementation not necessary; • Cannot predict who will benefit based on audiogram; • …benefit decreases as reverberation increases, etc; • LF compensation for losses> 40 dB

  17. Pumford et al., 2000 • Compared ITE and BTE performance • Complex sound field (5 speakers) • Improvement of 5.8 dB in SNR from omni to directional for BTE • Improvement of 3.3 dB in SNR from omni to directional for ITE • … but BTE had poorer omni performnace to start with...

  18. Novick et al, 2001 • The signal processing scheme has no measurable impact of the directional mic benefit • Trade-off from two hearing aids (omni) to one hearing aid (directional)

  19. Walter Reed group (JAAA) • Directional mode useful about 25% of the time (with experience); • User is capable of identifying environments where directional/ omnidirectional works best; • Report same level of satisfaction with either type of mic.

  20. What’s going on in my lab?

  21. North American Project • 10 sites across the country • 3 “subjects” at each site wearing a single-mic design on one ear and a two-mic design on the other ear • dsp versus analog transparent to user • Recheck of polars at 6, 12, 18 months (if we get that far...)

  22. Optimal pattern? (IJA) • Is one polar pattern superior either by group analysis or individual analysis? • 25 subjects fit with each of five mic con- ditions (omni, cardioid, hyper, super, & “monofit”) • Field data thrown out • Four directional conditions equal...

  23. Results • CST means and standard deviations for all subjects across microphone conditions measured in the anechoic chamber with an 8-speaker “diffuse” field noise source.

  24. Results • HINT means and standard deviations for all subjects across microphone condition measured in the anechoic chamber with an 8-speaker “diffuse” field noise source.

  25. Adaptive Mic Effective?(JASA) • Is the dynamic mic design (as implemented in the ClaroTM) effective? • Ten subjects tested with BTEs in anechoic and reverb environments • noise only in rear plane • overall 65 dBA but 2 second modulation (randomly) across five speakers

  26. Results • Same performance with fixed as with dynamic mode • Yet, each subject wore HAs for 3-4 weeks in home environments • They noted the “directional benefit” just not a difference in benefit in the dynamic mode; validation of lab data

  27. Digital noise reduction

  28. Four approaches to reducing noise

  29. 85 dB

  30. 85 dB 85 dB

  31. Sonic RE#_100101842 / Flat 50 dB Loss/ NR High/ Expansion OFF/85dB FONIX

  32. Sonic RE#_100101842 / Flat 50 dB Loss/ NR High/ Expansion OFF/85dB RANDOM

  33. Sonic RE#_100101842 / Flat 50 dB Loss/ NR High/ Expansion OFF/85dB BABBLE

  34. WIDEX DIVA#_018524 / Flat 50 dB Loss/ NR ON/ FEEDBACK CONTROL OFF/85dB FONIX

  35. WIDEX DIVA#_018524 / Flat 50 dB Loss/ NR ON/ FEEDBACK CONTROL OFF/85dB RANDOM

  36. WIDEX DIVA#_018524 / Flat 50 dB Loss/ NR ON/ FEEDBACK CONTROL OFF/85dB BABBLE

  37. Total RMS = -26.29 Total RMS = -16.49 Total RMS power = -18.89

  38. Will technological advances improve the outcome? • Depends on what you consider to be the advances… • Low/no distortion • Wide bandwidth • WDRC • On-line fitting help • Earmold-making techniques

  39. Will technological advances improve the outcome? • Feedback supression • Yes, in many cases • Directional microphones • With training/practice • Never as good as FM/ALD options • Digital noise reduction • For listening ease or comfort • I’m still hopin’

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