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1. Does Higher Technology Result in Higher Levels of Benefit? BCASLPA
October 22, 2004
Ruth Bentler
www.shc.uiowa.edu
2. What features? Dsp versus Analog
Directional Mics
Noise Reduction
Feedback Cancellation
3. Dsp versus Analog Orange Juice or Tomato Juice
Cardiovascular or Weight-Bearing
Puppy or cable
4. Dsp versus Analog Orange Juice or Tomato Juice
Cardiovascular or Weight-Bearing
Puppy or cable
5. 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)
6. 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…
7. 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
8. 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.
9. 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…
11. 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?
12. Directional Microphones?
13. What we know… One and two mic designs
Low frequency compensation
Mic noise goes up (and up)
Many companies use mic noise algorithm
14. 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
16. Directional Microphone
19. Polar Response Pattern
23. Head/pinna/torso effect
24. Head/pinna/torso effect
28. 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
29. Ways to quantify directivity Front-to-back ratio (FBR)
Directivity Index (DI)
Theoretical
Free field
KEMAR
30. Directivity Index (DI) DI can be represented as a function of frequency or an average across frequency. AIDI uses frequency weighting importance to represent and average DI.
DI can be represented as a function of frequency or an average across frequency. AIDI uses frequency weighting importance to represent and average DI.
35. 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
36. Laboratory Data AND, that lab data do not relate very well to self-report data
E.g., Walden, Surr & Cord (Hearing Journal, 2003)…
38. 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
39. 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
40. 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...
41. 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
42. 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)
43. 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.
44. Thus, the question of importance (to me!)
45. 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?
46. (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.
47. 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
48. 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
49. 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
50. Boymans and Dreschler (2000) continued “Subjective” outcome measures
Paired comparisons (only in the lab)
APHAB
51. 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!)
52. 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)
54. 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
55. Yueh, Souza, McDowell, Collins, Loovis, Hedrick, Ramsey, & Deyo, continued 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
56. Yueh, Souza, McDowell, Collins, Loovis, Hedrick, Ramsey, & Deyo, continued 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!
57. 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
58. 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
59. 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
60. Noise Reduction
61. 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”)
70. 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?
71. 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)
72. …if I could understand the titles…
73. 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
74. Data?
75. 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
76. 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
77. 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
78. Feedback Cancellation
79. 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…
80. 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?
81. Feedback Cancellation Do users of feedback cancellation schemes currently implemented in wearable hearing aids notice a
difference?
82. 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
83. Feedback Canceller: Gain MarginN=57 ears (19 @ U of MN;38 @ Starkey)
84. Again, with the phase cancellation provided by the Canta, the results were almost identical.Again, with the phase cancellation provided by the Canta, the results were almost identical.
85. For the hearing aid using a combination of band reduction and notch filtering, a reduction in energy from about 2700 to 4300 Hz is evident. This was on the order of approximately 8 to 10 dB in the most affected rangeFor the hearing aid using a combination of band reduction and notch filtering, a reduction in energy from about 2700 to 4300 Hz is evident. This was on the order of approximately 8 to 10 dB in the most affected range
86. These are spectra for the entire /i/ series processed through the Oticon Adapto. Recall that the data were filtered from 1000 to 7000 Hz. The results without the FBM activated (that is, at the original programmed level) are displayed in blue. The results with feedback controlled by the feedback manager are displayed in red.
The results are almost identical. Results in the 6000 Hz region are likely to be artifactual because they occur in the analyses of most all measurement conditions.These are spectra for the entire /i/ series processed through the Oticon Adapto. Recall that the data were filtered from 1000 to 7000 Hz. The results without the FBM activated (that is, at the original programmed level) are displayed in blue. The results with feedback controlled by the feedback manager are displayed in red.
The results are almost identical. Results in the 6000 Hz region are likely to be artifactual because they occur in the analyses of most all measurement conditions.
87. To summarize:
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.
To summarize:
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.
88. 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)
89. Answers Q1 No, not without consideration of the features
Q2 Maybe, although the issue of training needs further investigation
Q3 Maybe, but only in the sound quality/easy listening domain
Q4 No field data available, but this question may be answered by laboratory findings as well
90. 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.”
91. 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.”
92. 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.”