1. Objective Clinical Verification of Digital Hearing Aid Functions
4/15/2017
Colorado Academy of Audiology
Fall, 2009
Objective Clinical Verification of Digital Hearing Aid Functions
David J. Smriga, M.A.
Audiologist
Hearing Industry Consultant

2. Today’s Fitting Realities
In tough economic times, decisions are more carefully considered
Today’s sophisticated hearing instruments bring complexities to that decision-making process
An informed decision can not be made based on hearing instrument technology alone

3. Consider the Process
Your role is to make a decision about “which” hearing aid technology is best for the patient
Once selected, the fitting process shifts to the capabilities (the “logic”) of the fitting software
What happens if the fitting software doesn’t deliver an acceptable final result?

4. Subjective Authority
Based on impressions that may not always be consistent with better hearing
Too often, placed in the hands of the patient
Can compromise hearing aid utility
There can be a difference between what “sounds good” to the patient and what is in the best interests of the patient

5. The Fundamental Goal:
To render audible what the hearing loss has rendered inaudible
In particular, to build meaningful audibility of speech

6. Objective Measures of Aided Performance

7. The Hearing Review 2006 Dispenser Survey, June 2006, The Hearing Review

8. Hearing Journal Dispenser Survey, April, 2006, The Hearing Journal

9. Putting REM on Its Probe Tip!
Traditional REM Wisdom
Input Stimulus
PT sweep
Noise
Measure REIG curve
Adjust gain to hit a predicted insertion GAIN target
REM in the Digital World
Input Stimulus
Speech
“Dynamics”
Measure REAR speech banana
Adjust gain AND compression to deliver AUDIBILITY to THIS patient

10. Placing an “Audibility” Context on IG Targets
Take NAL-NL1 (for example):
Procedure seeks to amplify speech such that all bands of speech are perceived with equal loudness
However:
It derives IG targets assuming NOISE as a verification signal

11. For this compression hearing aid... Gain for speech @ Gain for tones
Oh good,
it doesn’t matter
which I use!

12. Output for speech is much less than output for pure tones.
4/15/2017
Output for speech is much less than output for pure tones.
Maybe you
should just
listen to
tones.

13. The output of a compression aid depends on the nature of its input signal

14. The output of a compression aid depends on the nature of its input signal

15. The output of a compression aid depends on the nature of its input signal

16. Speech Is An Excellent WDRC Measurement Stimulus
It IS the most important input signal that the patient will want to hear well and comfortably
It interacts with multi-band compressors in a more realistic way than tones
band interactions across frequency
changing intensity

17. The Terminology WE Will Be Using
REAR
Real Ear Aided Response
LTASS
Long Term Average Speech Spectrum
LTAS minima
Eardrum SPL exceeded 90% of the time
LTAS maxima
Eardrum SPL exceeded 10% of the time
RESR
Real Ear Saturation Response

18. Speechmap® Audibility Verification with Verifit

19. RECD Real-ear-to-coupler difference
The difference in dB across frequencies between the SPL measured in the real-ear and in a 2cc coupler, produced by a transducer generating the same input signal.
1) Recruitment
Accommodation

20. RECD Measurement How is it done?
Composed of 2 measurements: 2cc coupler measurement and real-ear measurement.
1) Recruitment
Accommodation

21. 4/15/2017
How do we measure RECD ?
Measuring the coupler response of the insert earphone

22. Measuring the real-ear response of the insert earphone..
4/15/2017
Measuring the real-ear response of the insert earphone..
Real-ear response
Coupler response
Average RECD
RECD

23. The Verifit uses the RECD to...
4/15/2017
The Verifit uses the RECD to...
Convert threshold and UCL obtained using insert earphones to SPL near the TM
Convert real-ear gain and output requirements to 2cc coupler targets
Convert test box measurements of hearing aid output to estimated real-ear aided response
(Simulated Real-Ear Measurements)
1) Recruitment
Accommodation

24. Understanding an SPLogram The Unaided SPLogram
Sounds get louder as you go UP the scale
Maximum output targets
Loud speech
Avg. speech
dB SPL Eardrum reference
Soft speech
Threshold (dB SPL TM)
Normal hearing
1) Recruitment
Accommodation

25. 30 dB

26. Now, let’s relate all of this back to fitting targets.

27. DSL 5.0a
Goal: to make speech audible for as broad a range of frequencies as possible
Output based targets
Incorporates average RECD and average REUG into target calculations
Targets are different than prior versions of DSL

28. NAL-NL1
Goal: To amplify speech such that all bands are perceived with equal loudness
Gain based, but modified by Audioscan to become an output target
Using the same adult average RECD and REUG used in DSL

29. Cambridge Aims Camfit Restoration Camfit Equalization
To amplify sounds that are soft, comfortable and loud to a normal hearing person so that they are soft, comfortable and loud for the HA wearer. (Stated goal of IHAFF fitting method).
Camfit Equalization
To amplify speech to produce the same loudness in each critical band. It has been argued that this is likely to give the highest intelligibility for a given overall loudness.

30. = DSL
= NAL
= CR
= CE

33. Speech Mapping of Open-Fit (Thin-Tube) Technology

34. Minimal Occlusion
Lybarger S. Earmolds. In: Katz J, ed. Handbook of Clinical Audiology, 3rd edition. Baltimore: Williams and Wilkins; 1985:

35. FIGURE 5: The pink shaded area is the eardrum SPL “speech banana” for 65dB speech input measured at the probe tip with the open-fit hearing aid turned OFF. The green shaded area is the eardrum SPL “speech banana” with the same hearing aid turned ON. The difference between the two indicates where amplification has reached the eardrum.

36. Verifying Digital Performance
2) Verifying Directionality Function

37. Laboratory Specification of Directionality
Polar Plots
-20
-15
-10 -5 15 30 45 60 75 90
105
120
135
150
165
180
195
210
225
240
255
270
285
300
315
330
345
360
2) Directional
Verification

38. Viewport: Digital Functions Summary/ Test Protocol Screen
Contains both
“Test Box” and
“On Ear” Options
4 quadrants – one
for each of the 4
digital functions
tests
Pre-set (but
adjustable)
protocols

39. Viewport Directional Test Quadrant - Open

40. Directional Frequency Response Input Stimulus
= Main input signal (512 pure tones 7.8Hz apart)
= Secondary input signal (512 pure tones 7.8 Hz apart)
Frequency (KHz)

41. Viewport Directional Test Box Result

42. Directionality Test (REM)
Verifit System
In REM Directional
Mode
Rear Facing Auxiliary Speaker
Subject
Aided Ear
With Probe
Tube Positioned
2) Directional
Verification

43. Verifying Digital Performance
3) Verifying Noise Reduction Function

44. Digital Noise Reduction Properties
Digital algorithm programmed to recognize “non-speech” elements of incoming stimulus
Operates independently in bands
Analyzes incoming signal modulation
Can vary in terms of time constants
Typically, slow attack, fast release
3) Noise
Reduction
Verification

45. Viewport Noise Reduction Test Box Quadrant - Open

46. Viewport Noise Reduction Test Result

47. Verifying Digital Performance
Feedback Reduction Function

48. Digital Feedback Reduction Properties
Active
Passive
Best
Overall
Application
Phase
Canceller
Poorest
Overall
Application
Notch
Filter

49. Key Factor of Concern
Does the feedback suppression function compromise hearing instrument performance when processing other stimuli?
4) Feedback
Reduction
Verification

50. Interactive Feedback Reduction Measurement

51. Viewport Feedback Test Box Quadrant - Open

52. Expected Display When Feedback is Induced By Monitoring Headset
1/3 ocatve
oscillation “humps”
Oscillation spikes

53. Viewport Feedback Box Test Result
Pink and green speech results
overlap with phase cancellation

54. Viewport Final Results Screen

55. Verifying Digital Performance
Frequency Lowering and Frequency Transposition Functions

56. The Concept Behind Changing Output Frequency Content
Some hearing losses have un-aidable regions where important speech information exists
Re-positioning input energy in these regions to regions that are aidable can provide access to these important speech ques

57. The Solution: Frequency Shifting
For many people with severe-to-profound hearing impairment in the higher frequencies, frequency shifting can improve signal audibility
Numerous different frequency lowering schemes have been developed and evaluated
Some of these schemes have been shown to improve speech understanding
Hugh McDermott, Professor of Auditory Communication and Signal Processing
University of Melbourne, Phonak Virtual Audiology Conference, May, 2009

59. Frequency Shifting Approaches
Frequency Transposition
Myirel Nyffeler, Speech Study Coordinator, Phonak Hearing Instruments, Switzerland,
Phonak Virtual Audiology Conference, May, 2009

60. Frequency Shifting Approaches
Frequency Transposition

63. Frequency Shifting Approaches
Frequency Compression

64. Frequency Shifting Approaches
Frequency Compression

66. Software Release V3.4 Main New Features
Frequency Lowering Verification

67. Frequency Lowering Input Stimuli

68. Frequency Lowering Test Result Example

69. Software Release V3.4 Main New Features
Frequency Lowering Verification
ISTS (International Speech Test Signal)
Incorporates the phonemic elements of several languages into a single speech test signal

70. Software Release V3.4 Main New Features
Frequency Lowering Verification
ISTS (International Speech Test Signal)
Incorporates the phonemic elements of several languages into a single speech test signal
New MPO Sweep Test Paradigm

71. Software Release V3.4
Targets now available in Audibility quadrant of Viewport
Can now download new software directly to SL operating system “stick”

72. Verifying Digital Performance
A Final Summary
Regarding Clinical
Verification

73. Recruitment Accommodation
Does It Work?
Verification of non-linear function relative to patients dynamic range using Speechmap DSL and multi-level measures.
Expediency: 5-10 minutes pre-ft. 5 minutes of fitting time
Is It Valuable?
Visual as well as auditory verification that soft speech is audible, average speech is comfortable and all sound fall appropriately within patient’s listening range

74. Directionality Function
Does It Work?
Multicurve display verifies function of directional system
Expediency: 3 minutes at fitting
Is It Valuable?
Both patient and spouse can “see” and “hear” the directional effect, either in the box or while on the patient’s ear

75. Noise Reduction Function
Does It Work?
Multicurve display verifies function of noise reduction system
Expediency: 3 minutes during fitting
Is It Valuable?
Both patient and spouse can “see” and “hear” noise reduction function either in the box or on the patient’s ear

76. Feedback Reduction Function
Does It Work?
Multicurve display helps verify function of FB system, and quantifies impact on other signal processing functions
Expediency: 5 minutes during fitting
Is It Valuable?
Patient judgement will be based on effectiveness of feedback control

77. Take-home Knowledge
Digital hearing aid functions can be verified in a routine clinical setting
Recruitment accommodation, directionality, noise reduction, feedback reduction
These properties can be effectively verified and demonstrated to the clinician, the patient and the spouse
These verification procedures are indeed clinically expedient
When implemented, these procedures can improve acceptance, reduce returns and substantiate value

78. References
ASHA Ad Hoc Committee on Hearing Aid Selection and Fitting (1998). Guidelines for hearing aid fitting for adults. American Journal of Audiology (7)1:5-13.
Abrahamson J (2001). Materials for Audiologic Rehabilitation: Help Getting Started. Hearing Review August 2001.
Cole WA, Sinclair ST (1998). The Audioscan RM500 Speechmap/DSL fitting system. Trends in Amplification 3(4):
Cornelisse LE, Seewald RC, Jamieson DG (1994). Wide-dynamic range compression hearing aids: The DSL[I/o] approach. Hearing Journal 47(10):23-26.
Csermak B, Armstrong S (1999). Bits, bytes & chips: Understanding digital instruments. Hearing Review January 1999:8-12.

79. References (cont.)
Frye GJ (2000). Testing digital hearing instruments. Hearing Review 7(8):30-38.
Frye G (1999). A perspective on digital hearing instruments. Hearing Review 6(10):59.
Harnack Knebel SB, Benter RA (1998). Comparison of two digital hearing aids. Ear & Hearing 19(4):
Hawkins DB, Cooper WA, Thompson DJ (1990). Comparison among SPLs in real ears, 2cm3 and 6cm3 couplers. Journal of the American Academy of Audiology 1:
Killion MC (2000). Compression: Distinctions. Hearing Review July 2000:44-48.
Kochkin S (2000). MarkeTrak V: Consumer satisfaction revisited. Hearing Journal 53(1):38-55.

80. References (cont.)
Kuk F (1999). Verifying the output of digital nonlinear hearing instruments. Hearing Review Nov. 1999:35-38,60-62,75.
Moodie KS, Seewald RC, Sinclair ST (1994). Procedure for predicting real-ear hearing aid performance in young children. American Journal of Audiology 3:23-31.
Mueller HG (2001). Probe-mic assessment of digital hearing aids? Yes, you can! Hearing Journal 54(1).
Mueller HG (2000). What’s the digital difference when it comes to patient benefit? Hearing Journal 53(3):23-32.
Newman CW, Sandridge SA (1998). Benefit from, satisfaction with, and cost effectiveness of three different hearing aid technologies. American Journal of Audiology 7(2):
Plomp R (1994). Noise, amplification and compression: Considerations of three main issues in hearing aid design. Ear & Hearing 15(1):2-12.
Pogash RR, Williams CN (2002). AudioInfos:59:30-34.

81. References (cont.)
Ross M (2000). Hearing aid research. Audiology Online Viewpoint
Scollie SD, Seewald RC, Cornelisse LE, Jenstad LM (1998). Validity and repeatibility of level-independent HL to SPL transforms. Ear & Hearing, 19:
Seewald RC (1998). Working toward consensus on hearing aid fitting in adults and children. Aural Rehabilitation and its Instrumentation (September):6-10.
The hearing care market at the turn of the 21st century. Hearing Review March 2000:8-24.
The 1999 hearing instrument market - The dispensers’ perspective. Hearing Review June 2000:8-45.
Valente M, Fabry DA, Potts LG, Sandlin RE (1998). Comparing the performance of the Widex Senso digital hearing aid with analog hearing aids. Journal of the American Academy of Audiology 9(5):
Venema TH (1998). Compression for clinicians. San Diego: Singular Publishing Group.

82. References
Dittberner, A.B. (2003). Misconceptions when estimating the directivity index for directional microphone systems on a mankin. International Journal of Audiology, 42(1), Dillon, H. (2001). Hearing aids: A comprehensive text. New York: Boomerang Press and Thieme. Pg 26, Pg Dillon, H. (2003) “Backgroung Noise – The Problem and Some Solutions” National Acoustics Laboratory, Presentation at Cochlear Implant and Hearing Aid Solutions Symposium
Elko, G.W. (2000). Superdirectional microphone arrays. In S.L. Gay & J. Benesty (Eds.), Acoustic signal processing for telecommuncation, (Chapter 10, pp ). Kluwer Academic Publishers. Flynn, M. C. & Lunner, T. (2005). Clinical verification of a hearing aid with artificial intelligence. The Hearing Journal, 58 (2), Killion, M.C. (2004). Myths about hearing in noise and directional microphones. The Hearing Review, 11(2). .

83. References (cont.)
Kirkwood, D.H. (2005). Dispensers surveyed on what leads to patient satisfaction. Hearing Journal, 58(4),
Knowles Electronics. Directional microphone applications, Knowles Application Note AN-4. Issue Lybarger, S.F. & Lybarger, E.H. (2000). A historical overview. In R. Sandlin (Ed.), Textbook of hearing aid amplification: Technical and clinical considerations, 2nd edition. San Diego, California: Singular Thomson Learning. Ricketts, T. & Mueller H.G. (1999). Making sense of directional microphones. American Journal of Audiology, 8,
Sound on Sound Recording Magazine, “Directional Microphones” September 2000 Issue, Cambridge, UK
Staab, W.J. (2002). Characteristics and use of hearing aids. In J. Katz, Handbook of clinical audiology, 5th Edition. Baltimore, Maryland: Lippincott, Williams and Wilkins. Pg
Staab, W.J. & Lybarger, S.F. (1994). Characteristics and use of hearing aids. In J. Katz, Handbook of clinical audiology, 4th Edition. Baltimore, Maryland: Lippincott, Williams and Wilkins.

84. References (cont.)
Strom, K.E. (2005). The HR 2005 dispenser survey. The Hearing Review, (12)6, Walden, B., Surr, R., Cord, M. & Drylund, O. (2004). Predicting hearing aid microphone preference in everyday listening. Journal of the American Academy of Audiology, 15,

85. References (cont.)
Ross M (2000). Hearing aid research. Audiology Online Viewpoint
Scollie SD, Seewald RC, Cornelisse LE, Jenstad LM (1998). Validity and repeatibility of level-independent HL to SPL transforms. Ear & Hearing, 19:
Seewald RC (1998). Working toward consensus on hearing aid fitting in adults and children. Aural Rehabilitation and its Instrumentation (September):6-10.
The hearing care market at the turn of the 21st century. Hearing Review March 2000:8-24.
The 1999 hearing instrument market - The dispensers’ perspective. Hearing Review June 2000:8-45.
Valente M, Fabry DA, Potts LG, Sandlin RE (1998). Comparing the performance of the Widex Senso digital hearing aid with analog hearing aids. Journal of the American Academy of Audiology 9(5):
Venema TH (1998). Compression for clinicians. San Diego: Singular Publishing Group.