Definition of gain. Real Ear Aided Gain = A - F. Real Ear Unaided d Gain = A - F. Real ear insertion gain = A U = REAG - REUG. Aidedd.

Transcription

1 Prescription of hearing aids for adults and children Harvey Dillon Teresa Ching, Gitte Keidser, Matt Flax, Richard Katsch Karolina Smeds, Justin Zakis Elizabeth Convery, Anna O Brien, Frances Lockhart, Emma VanWanrooy, Margot McLelland, Ingrid Yeend, Lydia Lai NAL CRC Hear The aim of amplification

2 Prescribe hearing aids to: Make speech intelligible Make loudness comfortable Prescription affected by other things localization, tonal quality, detection of environmental sounds, naturalness. Definition of gain U A F F Unaided Aidedd Real Ear Unaided d Gain = A - F Real Ear Aided Gain = A - F Real ear insertion gain = A U = REAG - REUG

3 Hearing aids amplify, so. How much amplification? Gain 5 db SPL 65 db SPL 8 db SPL Frequency Using prescription - easy

4 Adult Measure hearing thresholds h (db HL) Child Measure hearing thresholds h (db HL or db SPL) Measure individual RECD (or estimate from age) Enter into manufacturer software (hearing aid auto adjusted to approximate prescription) Enter into manufacturer software (hearing aid auto adjusted to approximate prescription) Verify with real ear measurement Adjust amplification i to better match prescription Adjust hearing aid in coupler via computer to better match prescribed coupler gain Infant Fitting Procedure Electrophysiological hearing threshold with insert phones (db nhl) Behavioural hearing threshold with insert phones (db HL) Measure individual RECD, (or estimate RECD from age) Calculate hearing threshold level (adult equivalent db HL or db SPL in ear canal) Apply prescription to derive coupler gain targets Verification of REAG? Evaluation! Adjust hearing aid via coupler/programmer to achieve coupler gain targets

5 Infant and Child Fitting Procedure Must be ear-specific hence insert Electrophysiological phones hearing threshold with insert phones (db nhl) Initial RECD will use probe in ear canal, or be estimated Can be ABR or ASSR, Behavioural hearing but must be earspecific Measure and individual threshold with insert phones (db HL) Estimation includes frequency-specific RECD, 1. Difference between (or electrophysiological estimate and behavioural RECD from thresholdsh age) 2. Measured or estimated RECD NAL-NL1 uses adult-equivalent Calculate hearing threshold hearing level (db HL) level DSLi/o] Apply uses canal prescription db SPLto (adult equivalent db HL or derive db SPL in ear canal) coupler gain targets RECD at time of fitting should use insert Measurement of the aid in Verification of phone coupled to the coupler should use REAG custom earmold broad-band? band test signals Adjust hearing aid via (or speech) coupler/programmer Evaluation! to achieve coupler gain targets Deriving a prescription

6 Two rationales for prescription p Normalize loudness at each frequency Maximize speech intelligibility while preventing excess total loudness NAL-NL1 NL1 and NAL-NL2NL2 Loudness normalization Uncomfortable Very Loud Loud Comfortable Normal Hearing (average) Soft Very Soft Inaudible Hearing Impaired (individual)

7 The rationale for NAL proceudres Maximize calculated speech intelligibility, but Keep total loudness less than or equal to normal NAL-NL1 (1999) empirical studies psychoacoustic studies speech intelligibility models NAL-NL2 Deriving optimal gains -step 1 Speech spectrum & level Loudness model Normal loudness Gain-frequency response Compare Intelligibility achieveded Intelligibility model Amplified speech spectrum Loudness model Loudness (hearing impaired) Audiogram

8 The audiograms Inverted hearing loss profiles used Rejection criterion : -3<= G <=6, where G is the slope sum(h(f))/3 <=1, where f is in the set {.5, 1, 2} khz The audiograms, continued

9 Deriving optimal gains -step 1 Audiogram 1 Speech level 1 Optimal gain frequency response Audiogram 1 Speech level 2 Optimal gain frequency response Audiogram 1 Speech level 3 Optimal gain frequency response Audiogram 2 Speech level 1 Optimal gain frequency response 2 audiograms x 6 speech levels 12 gain frequency responses, each at 2 frequencies from 125 Hz to 1 khz The result of step 1 Gain f HL f HL 3FA f SPL

10 Deriving optimal gains -step 2 Fit a four-dimensional equation to the data Gain at frequency f depends on: f, HL, HL 3FA, SPL Apply constraints: No compression for speech < 5 db SPL Low compression ratio for profound loss for fast compression Gain 5 Input SPL A workable formula G = [a + bh + ch 2 +d(h-h 3FA)] )].[1-e.SPL] ] a = a + a 1 log(f) b = b + b 1 log(f) + b 2 SPL c = c + c 1 log(f) d = d e = max (e, c max max )

11 The two key ingredients 1. A loudness model 2. An intelligibility model Calculating loudness Loudness model of Moore and Glasberg (24) Allowance for hearing loss External & middle ear Filtering into auditory bands Calculate loudness per band Sum across bands Free field speech level Input to cochlea Excitation level Loudness per band Total loudness

12 Predicting speech intelligibility SPL tave S 1/3 oct 3 Audibility: x x x x Importance: = = = = Freq =.3

13 Speech Intelligibility Index Sum SII = A I i i Audibility Importance But intelligibility gets worse if we make speech too loud! Speech intelligibility also depends on Level distortion Normal hearing gp people p perform poorer at high speech levels Level distortio on fact tor Speech level (db SPL)

14 SII = A I L i i i Level distortion factor Percen nt Co orrect The transfer function 1 Sentences Nonsense syllables Speech Intelligibility Index (SII)

15 Observed and Predicted performance correc ct Hz MF MS SF SS Pe ercent Sensation level (db) Ching, Dillon & Byrne, 1998 Speech intelligibility model Allowing for distortions in hearing loss

16 Subjects 2 adults with Audiogram -2 normal hearing 55 adults with sensorineural hearing loss mild to profound Experienced hearing aid users ) Hear ring thres shold leve el (db HL) Frequency (Hz) Speech perception p Stimuli: Filtered speech CUNY sentences 8 VCV syllables 6 Shaping: POGO prescription p Conditions: Le evel (db SPL) Quiet at high and low sensation levels Babble Noise Headphones: Sennheiser HD HP7 HP14 HP28 LP7 LP14 LP28 LP Frequency (Hz)

17 Audibility and Speech intelligibility N.H. 1. Percent correct versus VCVs.8 Propo ortion corr rect Calculated SII Q, LP7 N, LP7 Q, LP14 N, LP14 Q, LP28 N, LP28 Q, LP56 N, LP56 Q, HP28 N, HP28 Q, HP14 N, HP14 Q, HP7 N, HP7 May Reasons for scatter Scores in noise lower than scores in quiet Scores for older listeners lower than scores for younger listeners Scores for some bands consistently lower than scores for others

18 Audibility and Speech intelligibility H.I. 1. VCV.8 Propo ortion corre ect Calculated SII LP7: Q LP7: N LP14: Q LP14: N LP28: Q LP28: N LP56: Q LP56: N HP28: Q HP28: N HP14: Q HP14: N HP7: Q HP7: N Deficit = S ansii 1 ansii -SII eff Percen nt Co rrect Deficit = =.2 SII eff SII ansi Speech Intelligibility Index (SII)

19 VCV deficit vs CUNY deficit R=.77.1 NY SIIansi-S SIIeff CU VCV SIIansi-SIIeff Intelligibility and audibility 1 m p 3 Sensation level (db)

20 Variation of m with HL m 1. m p.5 m s Hearing Threshold (db HL) Parameters to optimise m p Criterion: Minimize error between observed intelligibility and predicted intelligibility log (f) m s p log (f) log (f)

21 Fitting the data a a 1 a 2 a 3 m s I(f) m p a 4 a 5 p m(f, HL) SII desensitized a 6 freq HL SPL(f) Optimizer results: 3 data sets BKB VCV CUNY Q & N

22 BKB, VCV and CUNY Desensitisation for hearing loss 1 Effecti ve audib bility Sensation level (db) fective ty Maximum eff audibilit hearing loss (db)

23 Why measure only pure-tone thresholds? Other measurements Hearing threshold levels Outer hair cell function click-evoked otoacoustic emissions Frequency resolution psychophysical tuning curves cochlear dead regions TEN test Cognitive ability Age

24 Healthy PTC no dead region Psychophysical tuning curve 11 A29 1 Masker Masker Le evel (db SPL) Signal Masker Frequency (Hz) Poor PTC: Dead region at 4 khz 12 Psychophysical tuning curve SPL) 11 Masker Level (db Masker Frequency (Hz)

25 Otoacoustic emissions Transient OAE 8 db SPL Non-linear (8 db / 7 db algorithm) Emission is octave filtered 5 Hz, 1 khz, 2 khz, 4kHz Pressure of filtered emission * r^2 Result is coherent emission strength Dead regions RIP NAL-NL1 only allows for hearing loss desensitization on average

26 Off-frequency frequency listening: TEN test Basila ar mem mbrane vibrat tion Threshold Equalizing Noise (TEN) Frequency or position Based on Moore (24) TEN elevation versus frequency TE EN Elevation (db) Frequency (Hz)

27 Cognitive ability Visual letter patterns Visual digit patterns Psychoacoustic correlations 4kHz Matrix Plot (Prof and Psy 11 March 9.sta 659v*75c) HL4k PTC4k_Q1 C4k El4k Cognition AgeLim

28 Psychoacoustic correlations 2kHz HL2k Matrix Plot (Prof and Psy 11 March 9.sta 659v*75c) PTC2k_Q1 C2k El2k Cognition AgeLim PTC Q factor versus HL (2 khz) khz Shifted tip In-place tip factor Tuning curve Q Hearing threshold (db HL)

29 Frequency resolution Degradation is greater at high h than at low frequencies, for the same degree of loss Reason: OHCs lost AFRI (db) AFRI (db) AFR RI (db) AF FRI (db) 6 35 Hz HTL (db HL) 6 1 khz HTL (db HL) 6 2 khz HTL (db HL) 6 4 khz HTL (db HL) Temporal resolution Resolution degrades more at tth the high hth than at the low frequencies, for the same degree of loss ATR RI (db) AT TRI (db) ATRI (db) Hz HTL (db HL) khz HTL (db HL) khz HTL (db HL) Reason: OHCs lost ATRI (db) khz HTL (db HL)

30 TEN elevation versus HL (2 khz) TE EN Elevatio on (db) Hearing threshold (db HL) OAE strength versus HL (2 khz) 1 5 OAE at 2 khz (db SPL) HL at 2 khz (db)

31 Tuning curve sharpness vs cognition PTC2k_Q Cognition (d') Correlations 5 Hz HL 5 PTC5_ Q1 OAE 5 TEN 5 Cognit Age HL PTC5_Q OAE TEN Cognition Age khz HL 1k PTC1k OAE TEN Cognit Age _Q1 1k 1k HL 1k PTC1k_Q OAE 1k TEN 1k Cognition Age kHz 4kHz HL 2k PTC2k OAE TEN Cognit Age HL 4k PTC4k OAE TEN Cognit Age _Q1 2k 2k _Q1 4k 4k HL 2k HL 4k PTC2k_Q PTC4k_Q OAE 2k OAE 4k TEN 2k TEN 4k Cognition Cognition Age Age

32 Correlations Age PTC HL OAE Cognit TEN Multiple regression including HL causes: correlations between age and PTC / OAE / TEN to disappear correlations between cognition and PTC / OAE / TEN to disappear PTC Age HL OAE Cognition TEN

33 Likely intermediate effects Cognition Mechanical? PTC Age Cardiovascular Noise Stria OHC OAE TEN IHC HL Can we better predict intelligibility if we use psychoacoustic results?

34 es-siieff (VCV Avg(QH QL N) LP56) Deficit (VCV & CUNY), HL, Q1, OAE, TEN, Cog, & Age: 56 Hz low pass SIIdes-SIIeff (CUNY Avg(QH QL N) LP56) L56HL Q1 LP56 COAE L56 EL LP56 Cogni tion AgeLim VCVs: Simple correlations with deficit after hearing loss correction Filter HTL PTC Q1 OAE strength TEN elev Cognit Age LP LP LP LP HP HP 14.33

35 CUNY: Simple correlations with deficit after hearing loss correction Filter HTL PTC Q1 OAE strength TEN elev Cognit Age LP LP LP 28 LP 56 HP HP Implications for prescription p Pure tone thresholds critical Knowledge of temporal resolution, frequency resolution, dead regions adds relatively little to prediction of intelligibility Age and cognitive ability affect all frequency bands similarly no effect on gain needed

36 Why are hearing thresholds so useful? Frequency selectivity Hearing thresholds Temporal resolution Central auditory processing Speech Perception proficiency Age Other Cognitive ability Empirical i evidence for prescription of gain- frequency response

37 Overall approach to prescription p Psychoacoustics Assumptions, rationale Theoretical predictions Final formula Speech science Compare Empirical observations Speech intelligibility vs Loudness normalization: Laboratory results NAL-NL1 preferred over loudness normalization NAL-NL1 objectively higher intelligibility in noise NUM BER OF SUBJECTS S NAL-NL1 IHAFF No preference P E RCENT S CORE NAL-NL1 IHAFF 5 Quiet Noise Quiet Traffic-noise 6 55

38 Speech intelligibility vs Loudness normalization: Field test results NAL-NL1 NL1 significantly preferred over loudness normalization two-channel better than single channel for sloping losses Numbe er of su ubjects IHAFF NL1 Withdr. Flat (mod/sev) Flat (mild) Steeply sloping National Acoustic Laboratories, Sydney, Australia Keidser and Dillon Gain; adults, medium input level (N = 187)

39 National Acoustic Laboratories, Sydney, Australia Keidser and Dillon Gain preference over time N = 11 Source: Keidser, O Brien, Yeend, & McLelland (submitted) National Acoustic Laboratories, Sydney, Australia Keidser and Dillon Gain; adults, low and high input levels om t 65 ation fro eferred a db ain devi gain pre SPL in d Pre eferred g NAL -NL1 re db Smeds et al. 26 Zakis et al. 27 Suggest that the compression ratio should be slightly higher, at least for clients with 5 mild 8 and moderate hearing loss Input level in db SPL

40 National Acoustic Laboratories, Sydney, Australia Keidser and Dillon Compression ratio preferences: severe and profound hearing loss 1.1 1/CR in LF band Average :1 18:1 1.8:1 31 3: Average HTL in LF band (db HL) Source: Keidser, Dillon, Dyrlund, Carter, and Hartley (27) National Acoustic Laboratories, Sydney, Australia Keidser and Dillon Adults congenital or acquired? eviation (db) gain de NAL-RP referred from N Pr Congenital (N=15) Acquired (N=28) LFA HFA

41 Language ability 12 months after fitting Hearing aids Effect of age of fitting: p =.1* Effect of hearing loss: p <.1* Effect of prescription: p =.9 Covariate means: F6AV3FAMD: EC-AC*"Cat2Fit"*"Cat2Pres"; LS Means EC-AC * Cat2Fit: F(1, 17)=7.741, p=.5 Vertical bars denote.95 confidence intervals 11 NAL DSL EC-AC A12P_EC EC-AC A12P_AC rd score (%) PL LS-4 Standar (n = 55) (n = 42) (n = 57) (n = 21) < 6 mo >= 6 mo < 6 mo >= 6 mo Fitting age category Fitting age category Adi digression i. At what age do you implant children?

42 Language at 6 and 12 months after implant Effect of implant age: p < *EC-AC*"Cat2CI"; LS Means Current effect: F(1, 31)=.6462, p=.812 Effect of Cat2CI: F =17.1, p =.2 Vertical bars denote.95 confidence intervals 6 mo post-implant 12 mo post-implant EC AC PLS-4 stan ndard score (%) <12mo (n=11) >=12 mo (n=22) <12mo (n=11) >=12 mo (n=22) Implant age Implant age Language skills at 3 yrs 12 Effect of age of implant: p =.2 EC-AC*"Cat2CI"; LS Means Current effect: F(1, 32)=4.2223, p=.4814 "Cat2CI": F= 5.32, p =.2 EC-AC CA36P_EC EC-AC CA36P_AC PLS-4 Stan ndard score (%) < 12 mo (n=9) >=12 mo (n=25) Implant age

43 Empirical evidence: variations from NAL-NL1NL1 Output level Children NAL-NL1 Adults Input level Prescribing amplification features

44 Intelligibility in noise Intelligibility in quiet Comfort & quality Convenience Clinicians Intelligibility in noise Amplification / tone controls Intelligibility in quiet Feedback cancelling Comfort & quality Convenience Clinicians

45 Intelligibility in quiet Wireless (e.g. FM) Intelligibility in noise Directional microphones Comfort & quality Convenience Clinicians Intelligibility in noise Intelligibility in quiet Transient noise suppression Adaptive noise suppression Multi-program Comfort Open fittings & quality Expansion Bilateral feedback control Active occlusion reduction Bilateral auto control Echo reduction Clinicians Convenience

46 Intelligibility in noise Intelligibility in quiet Comfort & quality Transient noise suppression Adaptive noise suppression Multi-program Open fittings Expansion Bilateral feedback control Active occlusion reduction Bilateral auto control Echo reduction Clinicians Convenience Intelligibility in noise Intelligibility in quiet Comfort & quality Bilateral manual control Phone interface Convenience Auto-telecoil Rechargeable battery Alerting tones and messages Clinicians

47 Intelligibility in noise Intelligibility in quiet Convenience Comfort & quality Bilateral manual control Phone interface Auto-telecoil Rechargeable battery Alerting tones and messages Clinicians Data logging Integrated RECD Intelligibility in noise Intelligibility in quiet Comfort & quality Convenience Data logging Integrated RECD Clinicians

48 Intelligibility in noise Intelligibility in quiet ADRO WDRC Auto-program Comfort & quality Convenience Auto-gain adaptation Trainability Clinicians Intelligibility in noise Wireless (e.g. FM) Directional microphones Intelligibility in quiet Amplification / tone controls Feedback cancelling Comfort & quality Convenience ADRO Adaptive noise suppression Bilateral manual control WDRC Multi-program Phone interface Auto- Open fittings program Auto-telecoil Expansion Implantable hearing aids Rechargeable battery Bilateral feedback control Auto-gain Alerting tones and messages adaptation Active occlusion reduction Trainability Bilateral auto control Echo reduction Data logging Integrated RECD Clinicians

49 Coming real soon. NAL-NL2 NL2 Shukron for listening

50 Not being used In the land of prescriptions. p Loudness scaling Electrophysiology PTCs Dead regions

51 VCV deficit vs tuning curve sharpness Uncorrected for HL: Dead regions marked.5.4 SIIans ii-siieff (VCV Avg(QH QL N) LP56) Q1 LP56 VCV deficit vs tuning curve sharpness Corrected for HL: Dead regions marked.5.4 SIIdes -SIIeff (VCV Avg(QH QL N) LP56) Q1 LP56

52 CUNY deficit vs PTC Uncorrected for HL: Corrected for hearing loss QL N) LP56) Ieff (CUNY Avg(QH SIIansii-SII eff (CUNY Avg(QH QL N) LP56) SIIdes-SIIe Q1 LP Q1 LP56 Yes, a little speech deficit increases as frequency selectivity gets broader But not once we fully build HL into the SII prediction

53 4. Experience Combined gender-experience experience effect f 3 Female new users prefer, on average, 3.7 db less gain than male experienced users

54 Binaural loudness summation Loudness adds across ears Total loudness = loudness left +loudness right Binaural loudness = 2.(monaural loudness) Loudness doubling: Low levels: 3 db High levels: 1 db Data for hearing impaired: Low levels: 3-4 db High levels: 5-1 db Implication: Binaural gain correction increases with input level Lo oudness (s sones) Level (db SPL) Binaural loudness summation For symmetrical loss: correction from 3 db to 8 db Bina aural co orrectio on (db) For asymmetical loss: less 4 Asymmetry db 1 db 2 db 3 db 5 1 Input level (db SPL)

55 EN leve el) in db SPL Tquiet, TE - max(t Tnoise PTC and TEN elevation: 2 Hz No shift Shifted tip Q1 at 2 khz Sharply tuned Psychophysical tuning curve and cochlear dead region: 4 khz 25 PTC and dead region: 4 Hz TEN lev vel) in db SPL ax(tquiet, Tnoise T - ma No shif t Shifted tip Q1 at 4 khz

56 TEN and PTC (non) agreement 2 khz TEN: Alive TEN: Dead TEN uncertain PTC: 6 1 Tip in place 1 PTC: Tip shifted PTC uncertain TEN and PTC (non) agreement 5 Hz TEN: Alive PTC: 62 1 Tip in place PTC: 12 Tip shifted TEN: Dead 1 khz TEN: Alive PTC: 65 2 Tip in place PTC: 8 Tip shifted TEN: Dead 2 khz TEN: Alive PTC: Tip in place PTC: Tip shifted TEN: Dead 4 khz TEN: Alive 6 1 PTC: Tip in place 4 3 PTC: Tip shifted TEN: Dead

57 BKB VCV CUNY Q N Psychoacoustical tuning curve: Q 1 A f AE Psychoacoustical tuning curve 34 Hz Level (db SPL) A M 1 db Q = F c / BW / Q 1 = 1/34 = 3.4 f Frequency (Hz) F c 5 1 1

58 Off-frequency frequency listening: PTC tion e vibrat mbrane ar mem Basila Frequency or position Off-frequency frequency listening tion e vibrat mbrane ar mem Basila Frequency or position

59 Cognition: words vs digits 5 Digits = *x 4 3 Digits Words