Does Higher Technology Result in Higher Levels of Benefit?

Does Higher Technology Result in Higher Levels of

Benefit? BCASLPA

October 22, 2004

Ruth Bentlerwww.shc.uiowa.edu

What features? Dsp versus Analog Directional Mics Noise Reduction Feedback Cancellation

Dsp versus Analog Orange Juice or Tomato Juice Cardiovascular or Weight-Bearing Puppy or cable

Dsp versus Analog Orange Juice or Tomato Juice Cardiovascular or Weight-Bearing Puppy or cable

Digital versus analog Not a debate amongst (most) researchers Easy to contrive the design Often misleads the clinician E.G.

Wood & Lutman (March 2004, IJA)

Abstract Question: Are dsp hearing aids better

than analog (linear) hearing aids? Design: 100 first-time users, single-

blinded, wore the HAs for 5 weeks each APHAB, GHABP, QoL, Diary REAR, Speech-in-Noise

Results…

Results Better dsp performance at 75 dB inputs

(4%); no difference at 65 dB input No difference in QoL No difference in use time No difference in APHAB subscales (n=36) Difference in Satisfaction subscale of

GHABP in favor of dsp 60 preferred dsp; 31 preferred analog

Conclusions “ Dsp provides significantly better speech

recognition performance for raised speech in background noise than carefully fitted (“but not adjusted”) linear analog hearing aids.”

“Users report somewhat greater satisfaction…and less aversiveness to sound.

An indepth look at the facts… Gain/output not controlled (audibility??) Limiting versus peak clipping not

controlled (distortion??) Linear aids not adjusted to “comfort”, as

were dsp aids (blinded??) And, finally, features such as directional

mics, noise reduction and feedback cancellation were active in the dsp circuits…

So, one more time…The advantages of dsp hearing

aids (to the end user) lie in the features, if they lie at all…Manufacturer benefits?Dispenser benefits?

Directional Microphones?

What we know… One and two mic designs Low frequency compensation Mic noise goes up (and up) Many companies use mic noise algorithm

Quick Tutorial Ways to build directivity into a hearing aid

case: Single mic with two ports Two omni mics Combination of omni & directional mics Three mics Mic array

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Directional Microphone

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Polar plot for omnidirectional mic in free field

OmnidirectionalOmnidirectional CardioidCardioid

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Polar Response PatternFree field characteristics of different types of microphones (Knowles TB 21)

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Dittberner, 2003

Dittberner, 2003

Head, Pinnae, and Torso Effects on Directional Microphones

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Wouters, 2003

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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 Adaptive directional mode

Ways to quantify directivity Front-to-back ratio (FBR) Directivity Index (DI)

Theoretical Free field KEMAR -10

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2,p is the magnitude of the off-axis mean-square sound pressure microphone response to a diffuse sound field.

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Laboratory Data We have 30-40 years of lab data and

trade-magazine evidence that Directional mics can improve SNR That enhancement is based on

# and placement of speakers Type/level/distance of noise Reverberation Baseline comparison (unaided, BTE/ITE, Omni) LF Compensation versus hearing levels

Laboratory Data AND, that lab data do not relate very well

to self-report data E.g., Walden, Surr & Cord (Hearing Journal,

2003)…

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Laboratory Data And, we can’t predict directional

advantage: Ricketts & Mueller (JAAA, 2000) examined three

studies for effect on directional advantage: Slope of hearing loss Amount of high frequency hearing loss Aided omnidirectional advantage

In one study, found significant negative relationship between aided omnidirectional performance and directional advantage

Cord, Surr, Walden & Olsen (2002) Performance of directional microphone hearing aids in everyday life, JAAA, 295-307.

Called back users of directional mic hearing aids that fell into two groups Those who used them regularly (deemed

successful)(n=22) Those who did not, and used the default

omnidirectional mode (deemed unsuccessful)(n=26)

No predictive power in APHAB scores

Cord, Surr, Walden & Olsen (2002)

Microphone Performance Questionnaire (MPQ) indicated directional mics preferred when signal is in front (near) and noise is in back

All 48 participants reported being satisfied with their HAs in each mic configuration; although the directional mic used less often, equally satisfied with it when they did...

Walden and Walden (2004). Predicting success with hearing aids in everyday living, JAAA, 342-353.

Purpose of the study: Investigate relationship between two measures of hearing aid success (IOI-HA and HAUS) and demographic and audiometric measures.

No blinding; clinic appointment data (n=50) Not really a comparison of mic conditions,

although IOI-HA showed statistically significant difference across

the groups Omni only (n=29) Omni/Directional with a switch (n=21)

NO difference in HAUS across two groups

Walden, Surr, Cord, and Dyrland (2004). Predicting hearing aid microphone preference in everyday listening. JAAA, 365-396.

Purpose of the study: Define environments for which either the omnidirectional or directional mode was better (thus providing guidance): Talker location Noise location Distance Time Ease of listening (Indirectly assigned reverberation)

Cord, Surr, Walden & Dyrland (2004)

Beginning of a model! Mean estimated use time was 61.8% for

omni mode and 38.2% for directional mode.

Average use of the omni mode was 65% for 8 participants for whom the default setting was omni, and 58.9% for the 9 participants for whom the default was directional.

Thus, the question of importance (to me!)

Do experienced/trained users of hearing aids with directional microphones report better amplification outcomes in daily life than users of hearing aids without directional microphones?

(Infamous) Valente, Fabry & Potts (1995).Recognition of speech in noise with hearing aids using dual microphones, JAAA, 440-449.

Purpose: To determine the effectiveness of a directional mic (two omni design)

Two sites (25 at each) No blinding Although not a comparison to omni

design, PHAB (Site 1) and APHAB (Site 2) showed subjects performing above the mean benefit norms.

Preves, Sammeth, & Wynne (1999). Field trial evaluations of a switched directional/omnidirectional ITE hearing instrument (1999). JAAA, 273-284.

Purpose: To evaluate the usefulness of a switch-option directional microphone system

10 blinded subjects (single-blinded cross-over design) wore aids for 2 trials

Self-report inventories (after non-equalized trial and equalized trial) APHAB Subjective Comments

Preves, Sammeth, & Wynne, continued For Trial #1 (non-equalized)

APHAB: RV subscale showed directional mode significantly better (fewer reported problems)

Comments: If only one, 6/10 directional mode; Subjects “hesitant to give up” either mode

For Trial #2 (equalized) APHAB: RV and BN RV subscale showed

directional mode significantly better (fewer reported problems)

Comments: If only one, 6/10 directional mode; Subjects “hesitant to give up” either mode

Boymans and Dreschler (2000), Field trials using a digital hearing aid with active noise reduction and dual-microphone directionality, IJA, 260-268.

16 subjects (single-blinded cross-over design) wore aids for four consecutive field trials No noise reduction Directional mics only Noise reduction only Directional mics plus noise reduction

Boymans and Dreschler (2000) continued

“ Subjective” outcome measures Paired comparisons (only in the lab) APHAB

Boymans and Dreschler (2000) continued

Aversiveness Subscale: Significantly fewer problems with the directional mic only condition over the omnidirectional mic condition

Evidence: A little (related to aversiveness) (Have to wait for the noise reduction

answer!)

Yueh, Souza, McDowell, Collins, Loovis, Hedrick, Ramsey, & Deyo (2001). Randomized trial of amplification strategies, Archives Oto, H&NS, 127:1197-1204

Purpose: To compare the effectiveness of an ALD, a non-programmable, non-directional hearing aid, and programmable directional hearing aid against the absence of amplification

60 subjects randomly assigned to four Tx groups (slight caveat here)

Yueh, Souza, McDowell, Collins, Loovis, Hedrick, Ramsey, & Deyo, continued

Self-report inventories used at baseline (before randomization) and at 1 and 3 mo: HHIE “Clinimetric” analysis of diaries APHAB Denver Scale of Communication Function Use time (recorded daily in diaries) Willingness to pay


HHIE: Significant difference in two hearing aid “tails” (P = .05) Standard (omnidirectional) Programmable (directional)

APHAB: Programmable significantly higher HHIE: Programmable significantly higher Willingness-to-pay

29% monthly income for standard 78% monthly income for programmable


HHIE: Significant difference in two hearing aid “tails” (P = .05) Standard (omnidirectional) Programmable (directional)

APHAB: Programmable significantly higher HHIE: Programmable significantly higher Willingness-to-pay

29% monthly income for standard 78% monthly income for programmabl

CAUTION!

Ricketts, Henry, Gnewikow (2003). Full time directional versus user selectable microphone modes in hearing aids, Ear & Hearing, 424-439.

Purpose: To examine benefit across omni and directional modes of hearing aid use Experienced, n = 15, cross-over design Blinding not possible

Self-report measures PHAB (6 subscales) New subscales

Source front (SF) Source back/localization (SB/L)

Log of usage

Within-subjects factor: Mic condition PHAB subscales: less benefit for omni in BN Two new subscales

SF: Less benefit for omni than full time or user-switchable directional

SBL: Less benefit for full time directional than omni or user-switchable directional

Use time

Evidence: A little

Palmer, Bentler, Mueller, and Powers (2005) Evaluation of a Second-Order Directional Microphone Hearing Aid:Self Report Outcomes (In Review)

49 subjects (within subject, before-after design) Self-report inventories only used to assess

benefit from amplification Diary was used to assist in differentiating

between omni, adaptive directional and fixed directional modes 34 of 49 had a preference (1/3, 1/3, 1/3) Evidence: Little

Noise Reduction

Noise Reduction From Dreschler, Verschuure, Ludvigsen,

Westerman, (IJA, 2001): Number of channels Time constants Degree of gain reduction as a function of

frequency Amount of noise reduction as a function of the

ratio between modulated and unmodulated components of the signal (“sensitivity”)

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Four approaches to reducing noise

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Widex (Diva)

Sonic Innovations

Siemens (Triano)

Starkey (Axent)

And so the important question… Do users of digital noise reduction

schemes currently implemented in wearable hearing aids report better amplification outcomes in daily life than users of hearing aids without noise reduction?

This effort… Noise reduction studies prior to 1995 Noise reduction studies since 1995 Total number of studies meeting criteria: 2.5

Peer-reviewed Self-report Blinded Appropriate design (n, statistics, etc)

…if I could understand the titles…

Olhede SC. Walden AT. Noise reduction in directional signals using multiple morse wavelets illustrated on quadrature Doppler ultrasound. IEEE Transactions on Biomedical Engineering. 50(1):51-7, 2003 Jan.

Thomas CG. Harshman RA. Menon RS. Noise reduction in BOLD-based fMRI using component analysis. Neuroimage. 17(3):1521-37, 2002 Nov

El-Mohri Y. Antonuk LE. Zhao Q. Maolinbay M. Rong X. Jee KW. Nassif S. Cionca C. A quantitative investigation of additive noise reduction for active matrix flat-panel imagers using compensation lines. Medical Physics. 27(8):1855-64, 2000 Aug

Data?

Walden, Surr, Cord, Edwards, Olson (2000). Comparison of benefits provided by different hearing aid technologies, JAAA,540-560.

40 HI subjects using Resound BZ5 Omni Dir NR + Dir

Field Ratings (for NR versus NR+Dir)No reported differences in speech understanding

Dir + NR rated significantly more comfortable than Omni

No difference in Sound Quality and Naturalness

Boymans and Dreschler (2000), Field trials using a digital hearing aid with active noise reduction and dual-microphone directionality, Audiology, 260-268.

Widex SENSO 16 HI subjects, single-blinded crossover design Lab data plus 3 consecutive field trials of 4

weeks each Self report via Dutch APHAB individual

items Significantly less aversiveness for sudden loud

sounds Significantly better understanding of speech in car

noise

Alcantara, Moore, Kuhnel, Launer (2003) Evaluation of the noise reduction system in a commercial digital hearing aid. IJA, 34-42.

Alcantara et al (2003) Eight experienced HI HA users wore new aid for

3 months No improvement for SRTs; no decrement for

sound quality while listening to four different kinds of background noise, all performed in the laboratory setting (“satisfaction with the noise reduction algorithm”)

Level of evidence: Weak/Low

Feedback Cancellation

What did we do? Roll off the highs Plug the vent Remake the earmold Turn down the VCW Dampen the peaks Adjust the gain in the narrow band Hold the mold in tighter…

Feedback Cancellation Do users of feedback cancellation

schemes currently implemented in wearable hearing aids report better amplification outcomes in daily life than users of hearing?

Feedback Cancellation Do users of feedback cancellation

schemes currently implemented in wearable hearing aids notice adifference?

This effort… Total number of related articles on feedback

cancellation: 20

Total number in IEEE Transactions: 8

Total number in peer-reviewed: 7

Total number published in JASA (no field data): 7

Total number meeting self-report critera: 0

Feedback Canceller: Gain MarginN=57 ears (19 @ U of MN;38 @ Starkey)

[U of MN data: Price and Nelson (2001)]

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Summary

• All feedback management systems evaluated allowed gain to be increased beyond the point of feedback

• The phase cancellation systems do not appear to affect the spectral components of speech when analyzed at the phoneme level.

• Band reduction and/or notch filtering affect the spectral components of speech when analyzed at the phoneme level.

Freed & Soli (2004 IHCON) How effective id the algorithm at preventing

oscilliation? How effective is the algorithm at reducing

oscillatory peaks? Does the algorithm sacrifice gain in any

frequency band? How robust is the algorithm when presented with

tonal input signals? Power Concentration Ratio (PCR) Aided Stable Gain (ASG) Extraneous Frequency Ratio (EFR)

AnswersQ1 No, not without consideration of the

featuresQ2 Maybe, although the issue of training

needs further investigationQ3 Maybe, but only in the sound

quality/easy listening domainQ4 No field data available, but this

question may be answered by laboratory findings as well

From Randall Robey (ASHA Leader, 2004):

“ Evidence may take many forms, from expert opinions to meta-analysis. Each form should not be equally persuasive that a certain (procedure) should become an aspect of recommended.”

“…the greater the scientific rigor, the more potent the evidence.”

From Christine Dollaghan (ASHA Leader, 2004): “The most common feeling seems to be …

anxiety that EBP will turn out to be one more unrealistic demand placed upon already over-burdened professionals.”

From Bentler at al. ( Ear and Hearing, 2003)

“Clinician is ethically obligated to accurately represent the potential benefits and advantages of (the) hearing aid.”

“This obligation can only be met by ongoing and critical review of the evidence supporting effectiveness.”

“(And) it is incumbent upon researchers to provide clinicians fair and accurate evaluations of new technologies.”

Documents

Does Higher Technology Result in Higher Levels of Benefit?