HD - Factors affecting HA prescriptioin

(Some) Factors affecting the prescription and adjustment of hearing aids : 

(Some) Factors affecting the prescription and adjustment of hearing aids Harvey Dillon NAL, CRC Hear 1st International Congress on Gerontology Stockholm June 2004

To download this talk: : 

To download this talk: www.NAL.gov.au After June 16

Who really did the work ….. : 

Who really did the work ….. Teresa Ching Frances Lockhart Emma Van Wanrooy Chris Brew Gitte Keidser Lydia Lai Wouter Dreschler Richard Katsch Karolina Smeds Liz Convery Justin Zakis Dillon, NAL

Overview : 

Overview Real life versus prescriptions The intelligibility of speech Desired loudness Acclimatisation effects Binaural loudness summation NAL-NL2 Client fine-tuning The Trainable Aid – the pressure’s off prescription Dillon, NAL

Fundamental differences : 

Fundamental differences Real life: Supra-threshold levels Broad-band signals Hearing aid prescription Threshold-based Narrow-band signals (pure tones) Dillon, NAL

Supra-threshold measures : 

Supra-threshold characteristics Supra-threshold measures Optimal amplification characteristics Supra-threshold measurements Hearing threshold measurements Estimated optimal amplification characteristics Dillon, NAL

Speech intelligibility : 

Speech intelligibility Teresa Ching, Frances Lockhart, Emma van Wanrooy, Lydia Lai, Chris Brew Dillon, NAL

Prescription and intelligibility : 

Prescription and intelligibility NAL-NL: response that maximises speech intelligibility Need to predict intelligibility for any gain-frequency response To prescribe accurately, we need to know how to predict speech intelligibility Prescription affected by other things (localization, tonal quality, detection, comfort, naturalness. Dillon, NAL

Slide 9: 

Freq 1/3 octave SPL 30 Threshold Noise Dillon, NAL

Slide 10: 

The transfer function Dillon, NAL

Speech intelligibility also depends on … Level distortion : 

Speech intelligibility also depends on … Level distortion Normal hearing people perform poorer at high speech levels Recent evidence suggests that degradation is greater at high than at low frequencies (Molis & Summers, 2003) Dillon, NAL

Slide 12: 

Observed and Predicted performance Ching, Dillon & Byrne, 1998 Dillon, NAL

Modified speech intelligibility index : 

Modified speech intelligibility index Hearing Loss Desensitization Ching, Dillon, Katsch & Byrne (2001) Dillon, NAL

Frequency resolution : 

Frequency resolution Dillon, NAL

Frequency resolution : 

Frequency resolution Severe and profound Outer hair cells mostly destroyed Frequency resolution much worse than normal Degradation is greater at high than at low frequencies Dillon, NAL

Temporal resolution : 

Temporal resolution Dillon, NAL

Temporal resolution : 

Temporal resolution Severe and profound Temporal resolution much worse than normal For the same degree of hearing loss, resolution degrades more at the high than at the low frequencies Dillon, NAL

Summary : 

Summary Speech intelligibility Frequency resolution Temporal resolution Hearing thresholds Dillon, NAL

What affects hearing loss desensitisation ? : 

What affects hearing loss desensitisation ? TRIadj FRIadj HTL.35k- HTL1k- HTL2k- HTL4k- Age CUI HTL HTL HTL HTL …….. Once we allow for the effects of hearing threshold at the same frequency Supra-threshold testing not worthwhile ! Dillon, NAL

Correlation of frequency and temporal resolution with speech intelligibility? : 

Correlation of frequency and temporal resolution with speech intelligibility? Progressive loss of frequency and temporal resolution as hearing loss progresses - high correlation with speech intelligibility With hearing threshold allowed for (“partialled out”), little further correlation between resolution and intelligibility, so NAL-NL1 based on thresholds. Then two new findings came along ……. Dillon, NAL

Slide 21: 

1. Dead regions NAL-NL1 only allows for hearing loss desensitization on average RIP Dillon, NAL

Off-frequency listening: TEN test : 

Off-frequency listening: TEN test Frequency Basilar membrane vibration Based on Moore (2004) Dillon, NAL

Off-frequency listening: PTC : 

Off-frequency listening: PTC Frequency Basilar membrane vibration Dillon, NAL

Off-frequency listening : 

Off-frequency listening Frequency Basilar membrane vibration Dillon, NAL

Slide 25: 

No dead regions HLD and Cochlear dead regions SII over-estimated performance of people with dead regions (Baer et al, JASA, 2002) Predicted Measured Dillon, NAL

Audiograms: with and without dead regions(Vickers et al., 2001; Baer et al., 2002) : 

Audiograms: with and without dead regions(Vickers et al., 2001; Baer et al., 2002) Dillon, NAL

Slide 27: 

2. Desensitization in noise Dillon, NAL

Different HLDs for quiet vs noise? : 

Different HLDs for quiet vs noise? Quiet Noise Source: Hogan & Turner, 1998; Turner & Henry, 2002 Yes! Dillon, NAL

Hearing loss desensitization and frequency resolution : 

Hearing loss desensitization and frequency resolution Ability to extract Speech information From an audible signal Dillon, NAL

Subjects : 

Subjects 20 adults with normal hearing 59 adults with sensorineural hearing loss mild to profound Experienced hearing aid users Dillon, NAL

Method : 

Method Hearing threshold levels Outer hair cell function click-evoked otoacoustic emissions Frequency resolution psychophysical tuning curves cochlear dead regions – TEN test Speech perception in quiet and noise consonants sentences Dillon, NAL

Speech perception : 

Speech perception Stimuli: Filtered speech CUNY sentences VCV syllables Shaping: POGO prescription Conditions: Quiet at high and low sensation levels Babble Noise Headphones: Sennheiser HD25 Dillon, NAL

Audibility and Speech intelligibility: Preliminary analysis : 

Audibility and Speech intelligibility: Preliminary analysis Preliminary analysis Dillon, NAL

Slide 34: 

Dillon, NAL

Proficiency = SA / S : 

Proficiency = SA / S 0 20 40 60 80 100 0 0.2 0.4 0.6 0.8 1 Speech Intelligibility Index (SII) Percent Correct ? Proficiency= 0.3/0.6 = 0.5 Dillon, NAL

Psychoacoustical tuning curve: Q10 : 

Psychoacoustical tuning curve: Q10 Q = Fc / BW Q10 = 1000/340 = 3.4 Fc Dillon, NAL

Healthy PTC – no dead region : 

Healthy PTC – no dead region Dillon, NAL

Poor PTC: Dead region at 4 kHz : 

Poor PTC: Dead region at 4 kHz Dillon, NAL

Psychophysical tuning curve and cochlear dead region: 2 kHz : 

Psychophysical tuning curve and cochlear dead region: 2 kHz Sharply tuned Dillon, NAL

Slide 40: 

Psychophysical tuning curve and cochlear dead region: 4 kHz Dillon, NAL

Does frequency selectivity affect speech proficiency? : 

Does frequency selectivity affect speech proficiency? Dillon, NAL

Speech proficiency vs tuning curve sharpness: low pass : 

Speech proficiency vs tuning curve sharpness: low pass Poor tuning Sharp tuning Dillon, NAL

Slide 43: 

Speech proficiency vs tuning curve sharpness: low pass Poor tuning Sharp tuning Dillon, NAL

Slide 44: 

Speech proficiency vs tuning curve sharpness: high pass Dillon, NAL

Yes – speech proficiency decreases as frequency selectivity gets broader : 

Yes – speech proficiency decreases as frequency selectivity gets broader There is at least as much need to allow for hearing loss desensitization in noise as in quiet Dillon, NAL

Does hearing threshold loss affect speech proficiency? : 

Does hearing threshold loss affect speech proficiency? Dillon, NAL

Speech proficiency versus hearing loss: low pass : 

Speech proficiency versus hearing loss: low pass Dillon, NAL

Speech proficiency versus hearing loss: low pass : 

Speech proficiency versus hearing loss: low pass Dillon, NAL

Speech proficiency versus hearing loss: high pass : 

Speech proficiency versus hearing loss: high pass Dillon, NAL

Yes – speech proficiency decreases as thresholds increase : 

Yes – speech proficiency decreases as thresholds increase Dillon, NAL

Does age affect speech proficiency? : 

Does age affect speech proficiency? Dillon, NAL

Distribution of ages : 

Distribution of ages Dillon, NAL

But …. : 

But …. Age Hearing threshold Frequency selectivity Dillon, NAL

Effect of age : 

Multi-linear step-wise regression Dependent variable = Proficiency factor Independent variables = Hearing thresholds Age category Frequency selectivity (Q10 from tuning curve) Otoacoustic emission strength Elevation in TEN test Effect of age Dillon, NAL

Multi-linear regression results : 

Multi-linear regression results Dillon, NAL

Effect of age: HP 700 Hz : 

Effect of age: HP 700 Hz Dillon, NAL

Effect of age: HPF 2800 Hz : 

Effect of age: HPF 2800 Hz Dillon, NAL

Effect of age: LPF 700 Hz : 

Effect of age: LPF 700 Hz Dillon, NAL

Multi-linear regression results : 

Multi-linear regression results Dillon, NAL

In most cases age did not affect speech intelligibility, once hearing loss had been allowed for : 

In most cases age did not affect speech intelligibility, once hearing loss had been allowed for ……. But these are research subjects! Dillon, NAL

Results summary : 

Results summary Ability to use speech information decreases with increased hearing loss Degradation greater at high than at low frequencies Degradation in noise at least as great as in quiet Higher proficiency associated with better frequency resolution (Q10) Partial relation between Q10 and cochlear dead region Only a minor effect of age demonstrated / desired loudness Dillon, NAL

Slide 62: 

Desired Loudness Karolina Smeds, Justin Zakis, Gitte Keidser, Liz Convery, Frances Grant Dillon, NAL

Desired loudness : 

Desired loudness NAL-NL1 aims at normal overall loudness. What do people want compared to NAL-NL1? Can also compare to NAL-RP Dillon, NAL

Preferred gain relative to prescription : 

Preferred gain relative to prescription Clinician survey: 39 clinicians - estimate the proportion of clients who change gain Too soft – 8%; Just right – 71%; Too loud – 21% Dillon, NAL

Desired loudness : 

Desired loudness Direct experiments – Smeds et al Adjustment of gain in lab, and in the field Dillon, NAL

Rated loudness - lab : 

Rated loudness - lab Dillon, NAL

Desired loudness re normal in lab : 

Desired loudness re normal in lab Dillon, NAL

Loudness at desired volume setting : 

Loudness at desired volume setting Dillon, NAL

Desired loudness – field : 

Desired loudness – field Hearing impaired subjects Dillon, NAL

Desired loudness in field : 

Desired loudness in field Normal hearing subjects Dillon, NAL

Desired loudness : 

Desired loudness Dillon, NAL

Gain deviation from NAL-NL1: Zakis : 

Gain deviation from NAL-NL1: Zakis Dillon, NAL

Slide 73: 

Acclimatization to gain Liz Convery Dillon, NAL

Acclimatization to gain : 

Acclimatization to gain Literature search …… Dillon, NAL

Slide 75: 

Binaural effects Dillon, NAL

Binaural interactions : 

Binaural interactions Binaural interference: minority of elderly (perhaps 10%) [Jerger et al 1993; Siegenthaler & Craig, 1981] may arise from cochlear distortion simulations [Hood & Prasher 1990] diplacusis [Markides 1977, 1982] loss of efferent control of OHC [LePage 1989; Rajan 1995; Scharf et al 1994] loss of transfer between hemispheres (in corpus callosum) left ear deficiency on diotic and dichotic word scores, symmetrical pure tone thresholds, ABR wave V latencies & amplitudes [Chmiel et al 1997] To NAL-NL2 / fine tuning Dillon, NAL

Slide 77: 

Patient fine-tuning Wouter Dreschler, Gitte Keidser, Liz Convery Dillon, NAL

Patient fine-tuning : 

Patient fine-tuning Two loudspeakers and a TV-screen Binaural presentation With or without hearing aids Dillon, NAL

Controller types : 

Controller types Dillon, NAL

Slide 80: 

Dillon, NAL

Preferred gain relative to NAL-RP prescription : 

Preferred gain relative to NAL-RP prescription Reasonable similarities between the overall results for different controllers Consistent differences across listening environments Dillon, NAL

The starting baseline affects the apparent preference! : 

The starting baseline affects the apparent preference! The effect occurs almost equally for all video’s Flatter starting response Steeper starting response Dillon, NAL

The starting baseline affects the apparent preference! : 

The starting baseline affects the apparent preference! The effect occurs almost equally for all controllers Dillon, NAL

But not all “preferred” results are equally good! : 

But not all “preferred” results are equally good! / trainable aid Dillon, NAL

Slide 85: 

NAL-NL2 Richard Katsch, Teresa Ching Dillon, NAL

NAL-NL2 : 

NAL-NL2 Altered loudness targets: less than normal loudness, especially for inputs > 65 dB SPL Altered desensitisation: amount unknown May add supplementary supra-threshold tests? Prescriptions at all levels, frequencies and hearing losses Higher gain for congenitally impaired children? Probably still no acclimatization steps To end / Trainable aid Dillon, NAL

Moving away from prescriptions : 

Moving away from prescriptions The trainable hearing aid Justin Zakis, Gitte Keidser, Hugh Mcdermott, Liz Convery Dillon, NAL

Slide 88: 

Aid user adjusts settings... Trainable Aid Dillon, NAL

Slide 89: 

Aid user adjusts settings... Trainable Aid Dillon, NAL

Slide 90: 

...then presses voting button Trainable Aid Dillon, NAL

Slide 91: 

Process repeats for other sounds Trainable Aid Dillon, NAL

Slide 92: 

After training, preferred settingsare automatically applied... Trainable Aid Dillon, NAL

Slide 93: 

Trainable Aid After training, preferred settingsare automatically applied... Dillon, NAL

Slide 94: 

Trainable Aid After training, preferred settingsare automatically applied... Dillon, NAL

Slide 95: 

Trainable Aid After training, preferred settingsare automatically applied... Dillon, NAL

Slide 96: 

First and Second Comparison Trial Results * p < 0.05 ** p < 0.01 Only S201 had a statistically significant difference in scores between comparison trials (p = 0.0176) Dillon, NAL

Trainable aid philosophy : 

Trainable aid philosophy Prescribe what can be prescribed, automatically and in minimum clinical time Leave the rest to the client (and the intelligence of the hearing aid) Dillon, NAL

Slide 98: 

……… thanks for listening www.nal.gov.au