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

OmnidirectionalCardioid Hypercardioid Supercardioid Polar Response Pattern Free field characteristics of different types of microphones (Knowles TB 21)

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.)

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

Adaptive Directionality

Adaptive Directionality

Adaptive Directionality

Adaptive Directionality

Adaptive Directionality

Adaptive Directionality

Adaptive Directionality

Adaptive Directionality

In a diffuse field…

Ricketts & others ( ) 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

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...

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)

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.

What’s going on in my lab?

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...)

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...

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.

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.

Adaptive Mic Effective? (JASA) Is the dynamic mic design (as implemented in the Claro TM ) 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

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

Digital noise reduction

Four approaches to reducing noise

85 dB

Sonic RE#_ / Flat 50 dB Loss/ NR High/ Expansion OFF/85dB FONIX

Sonic RE#_ / Flat 50 dB Loss/ NR High/ Expansion OFF/85dB RANDOM

Sonic RE#_ / Flat 50 dB Loss/ NR High/ Expansion OFF/85dB BABBLE

WIDEX DIVA#_ / Flat 50 dB Loss/ NR ON/ FEEDBACK CONTROL OFF/85dB FONIX

WIDEX DIVA#_ / Flat 50 dB Loss/ NR ON/ FEEDBACK CONTROL OFF/85dB RANDOM

WIDEX DIVA#_ / Flat 50 dB Loss/ NR ON/ FEEDBACK CONTROL OFF/85dB BABBLE

Total RMS power = Total RMS = Total RMS =

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

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’