Power Instruments, Power sources: Trends and Drivers. Steve Armstrong September 2015

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1 Power Instruments, Power sources: Trends and Drivers Steve Armstrong September 2015

2 Focus of this talk more significant losses

3 Severe Profound loss Challenges Speech in quiet Speech in noise

4 Better Listening in Quiet Figure 2. Relationship between pure-tone average and ability to understand speech in quiet. Blue circles are listeners with mild to moderate loss; red circles are listeners with moderately-severe to severe loss.

5 Better Listening in Noise Figure 3. Relationship between pure-tone average and ability to understand speech in noise. Blue circles are listeners with mild to moderate loss;red circles are listeners with moderately-severe to severe loss.

6 Louder speech reduces intelligibility even for normal hearing listeners

7 Auditory filter

8 Severe Profound loss Challenges Speech in quiet Speech in noise OHC loss Quieter sounds less audible Broader filters IHC loss Less signal passed on to Brain Neural starvation Dead regions

9 Drop off in Effectiveness of Audibility

10 Effective audibility Desensitization for hearing loss Sensation level (db) 0 dbhl 20 dbhl 40 dbhl 60 dbhl 80 dbhl 100 dbhl 120 dbhl

11 Broader Auditory filters Less selectivity in the frequency domain Poorer peripheral filtering Puts more emphasis on the Temporal cues Envelope cues Temporal Fine Structure TFS

12 Outer Ear Model of the periphery IHC AN Brain OHC Nature s WDRC wiring Nature s Analog to Digital Convertor

13 The solid line shows a schematic illustration of an input output function on the basilar membrane for a tone with frequency close to CF. The dashed line shows a linear input-output function. Moore B C J Br Med Bull 2002;63: by Oxford University Press

14 the Envelope

15 the Fine Structure

16 Audibility Important but not sufficient Requires gain and output Reduced dynamic range available Improve Signal to Noise Ratio Directional Microphones Noise Reduction

17 Compression for severe and profound hearing loss : Average 1/CR in Average HTL in LF band (db HL) Source: Keidser, Dillon, Dyrlund, Carter, and Hartley (2007) 1.8:1 3:1

18 High Frequency CR 1:1 1.8:1 3:1

19 Compression speed slower is better Souza, P., Jenstad, L., & Folino, R. (2005) Figure 5. Nonsense syllable recognition with fast-acting (5 ms attack time, 100 ms release time) or slowacting (500 ms attack time, 5 sec release time) compression for 22 listeners with severe hearing loss. Results are shown for 3 input levels: 50, 65, and 80 db SPL. Performance is significantly poorer with the fast compression at 50 and 65 db SPL. There was no difference in scores at 80 db SPL. This is attributed to activation of the compression limiter, which temporally distorts the signal.

20 is Audibility always a good thing? Dead Regions The audiogram says we have a threshold But the patient is actually listening to Off Place effects No contribution to intelligibility May contribute to distortion

21 Outer Ear Dead Regions IHC AN Brain OHC

22 Steeper Audiograms warrant more caution

23 Dead Regions Reduce gain 1.7 x start of drop off Frequency lowering

24 HA features Gain FBC WDRC EQ something has allow for more Gain! Directional Mics NR Single ear Wireless multi mic improves Ease of Listening Freq Lowering Jury is still out

25 Power Sources

26 The challenges High Power Instruments need omph High output levels require low impedance receivers Draw lots of current providing loud outputs Especially true in the low frequency regions Wireless technologies 2.4 GHz requires more power then NFMI Bursty activity means even higher peak currents

27 Wireless options 2.4 GHz RF 5 ma. while streaming audio NFMI ( 3 12 MHz ) 3 ma. while streaming audio Telecoil ( 100 Hz 10 khz ) 1 ma little change

28 HA battery technology Zinc Air most popular Watt-hours = Voltage*capacity 750 mwh = 1.25V * 600 mah Volume measured in milliliters Watt-hours / milliliter

29 Energy Sources Gasoline 9.7 Wh/mL Methanol 4.7 Wh/mL 35% eff 1.6 Wh/mL Zinc Air 1.4 Wh/mL Hydrogen 0.4 Wh/mL Li-ion 0.3 Wh/mL NiMH 0.3 Wh/mL Silver Zinc 0.3 Wh/mL

30 zpowerbattery.com

31 Spec sheet

32 Voltage over discharge

33 Compared to Zinc Air

34 Gain and Output depend on battery voltage + 5 db -3 db

35 HA schematic DSP Amplifier Microphone Receiver - Speaker Battery

36 add a new Voltage Regulator DSP Amplifier Switching Voltage Regulator

37 Zinc Air Highest energy density Design balance makes predicting performance slightly more difficult Performance variations Brand to Brand Temperature/humidity sensitive

38 Rechargables Run time drops off with number of recharge cycles all of them do! Built in or removable? Recharge in HA or external Only get 1 year of realistic life User changeable? Send back to Manufacturer?

39 questions or an electronic handout Steve Armstrong

Prescribe hearing aids to:

Prescribe hearing aids to: Harvey Dillon Audiology NOW! Prescribing hearing aids for adults and children Prescribing hearing aids for adults and children Adult Measure hearing thresholds (db HL) Child Measure hearing thresholds