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Mild Hearing Loss is Serious Business Harvey Dillon Sharon Cameron, Teresa Ching, Helen Glyde, Gitte Keidser, David Hartley, Jorge Mejia NAL, The Hearing.

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Presentation on theme: "Mild Hearing Loss is Serious Business Harvey Dillon Sharon Cameron, Teresa Ching, Helen Glyde, Gitte Keidser, David Hartley, Jorge Mejia NAL, The Hearing."— Presentation transcript:

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2 Mild Hearing Loss is Serious Business Harvey Dillon Sharon Cameron, Teresa Ching, Helen Glyde, Gitte Keidser, David Hartley, Jorge Mejia NAL, The Hearing CRC IHCON, 2010

3 Slides on the NAL web site:

4 What is mild hearing loss? Four-frequency average (500, 1000, 2000, 4000 Hz) hearing loss in better ear between 20 and 40 dB HL Self-reported disability or handicap within a certain range SRT in noise loss of between 3 and 6 dB

5 4FAHL or 3FAHL?

6 How prevalent is mild hearing loss?

7 Davis (1995): 16% of adult population Wilson (1990): 18% of adult population Hartley et al (in press): 34% of people aged > 50 years

8 Blue Mountains 4FAHL better ear Hartley et al (in press)

9 Aging population - Australia

10 Population aging, worldwide

11 Hearing loss distribution (3FAHL better ear) OHS population BMHS population

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13 Mild losses for study Mild loss (4FA=29 dB) Mild-mod loss (4FA=39 dB) ~ Minimum loss eligible for government benefits ~ Median loss newly fitted in Australia

14 Mild losses for study Mild 9 dB Mild-mod 39 dB Moderate 49 dB Mod-Sev 59 dB Severe 69 dB 4FA HL

15 How common is hearing aid use amongst those with mild hearing loss?

16 Penetration by hearing loss Penetration as a function of hearing loss –Davis (1995) –Wilson et al (1998) –Hartley et al (in Press) –Kochkin consistent

17 Aid ownership by hearing loss Blue Mountains Population >55 years Hartley et al (in Press)

18 What are the characteristics of mild hearing loss?

19 Characteristics of mild loss Threshold elevation √ Loss of OHC/OAE Loss of frequency resolution – TEN, PTC, FRI Loss of temporal (envelope) resolution Loss of fine temporal information Loss of spatial processing Loss of SRT in noise Increased disability and handicap

20 Loss of active process in cochlear: OHC and OAE

21 Loss of frequency resolution f A f A FRI Ching & Dillon (unpublished data)

22 Frequency resolution

23 Loss of temporal resolution A t t TRI

24 Temporal resolution Ching & Dillon (unpublished data)

25 Loss of fine temporal information 20 synapses per IHC Synapse loss or IHC loss  reduced averaging  temporal jitter Inspiration: Bodian, Lieberman, Moore, Pichora-Fuller, Spoendlin,

26 A digression into “normal” hearing

27 Spatial Processing Disorder 26 Noise Speech Sharon Cameron

28 Listening in Spatialised Noise - Sentences (LiSN-S) Conditions Total Advantage Talker Advantage Spatial Advantage High Cue Low Cue Same voices Different voices Same direction Different directions Cameron & Dillon (2009)

29 LiSN-S Diagnostic Screen

30 Spatial Advantage (≡ Spatial Release from Masking) Better Australia Nth America

31 Spatial Advantage Better

32 Results profile: spatial processing disorder

33 Spatial processing remediation Pre vs. Post (n=9) LC SRT - p = Talker Advantage - p = HC SRT - p = Spatial Advantage - p = Total Advantage - p = 0.001

34 Application to people with hearing loss

35 Spatial hearing loss in hearing-impaired people: LiSN-S Prescribed Gain Amplifier

36 Deficit in SRT n with hearing loss Cameron, Glyde & Dillon, unpublished data) R = P =

37 Cause of deficit in SRT n R = P = Cameron, Glyde & Dillon, unpublished data)

38 Talker advantage deficit versus age Cameron, Glyde & Dillon, unpublished data)

39 Binaural processing ILD ITD L R Executive control x x CAPD ~ Sensorineural hearing loss ILD ITD CN SO / IC / A1

40 Loss of SNR in understanding speech “Basic” loss of 0.6 dB per 10 dB of loss + Loss of Spatial release from masking of 2.3 dB per 10 dB of loss + Loss of Talker cue release from masking of 0.5 dB per 10 years of age

41 Loss of SRT in noise Commonly 1.5 dB increase in SNR per 10 dB of hearing loss 1 dB / 10 dB 1.8 dB / 10 dB SNR = -4 dB Carter, Zhou & Dillon, unpublished data)

42 Should mild hearing loss interfere with speech perception?

43 Speech and noise levels Source: Pearsons, Bennett and Fidell (1977) SNR

44 Calculation of SII Noise = 60 dBA Speech = 64 dBA SII nh =0.65 SII hi =0.46

45 Effective audibility

46 Transfer function SII  Percent correct

47 Mild losses for study Mild loss (4FA=29 dB) Mild-mod loss (4FA=39 dB)

48 Predicted speech intelligibility Greatest problems in noisy places !!

49 Predicted variation of SRT n with hearing loss Modified SII model predicts only 0.4 dB loss per 10 dB of hearing loss Speech level

50 Modification of SII Assume normal hearers get 6 dB advantage from spatial separation of speech and noise Assume hearing impaired listeners lose spatial advantage at a rate of 1.3 dB per 10 dB of loss (above SII predictions)  total loss of SNR is 1.7 dB per 10 dB of loss

51 Calculation of intelligibility Speech spectrum Noise spectrum Threshold Sensation Level Effective audibility Importance function SII (Information received) Percent correct Max

52 Do hearing aids help people with mild hearing loss? current ^

53 Benefit of hearing aids Predict increase in speech intelligibility with the modified Speech Intelligibility Index

54 Calculation of aided benefit Noise = 50 dBA Speech = 58 dBA

55 Speech intelligibility (mild loss) Hearing aid “helps” in quiet places Tiny additional benefit from directivity Conditions: DI = 3 dB when REIG > 3 dB n.h. spatial adv = 6 dB ∆SNR re n.h. = -3.7 dB

56 Speech intelligibility (mild-moderate loss) Hearing aid “helps” in quiet places Tiny additional benefit from directivity Conditions: DI = 3 dB when REIG > 3 dB n.h. spatial adv = 6 dB ∆SNR re n.h. = -5.1 dB

57 Speech intelligibility (moderate loss) Conditions: DI = 3 dB when REIG > 3 dB n.h. spatial adv = 6 dB ∆SNR re n.h. = -6.5 dB

58 Speech intelligibility (moderate-severe loss) Conditions: DI = 3 dB when REIG > 3 dB n.h. spatial adv = 6 dB ∆SNR re n.h. = -7.7 dB

59 Speech intelligibility (severe loss) Conditions: DI = 3 dB when REIG > 3 dB n.h. spatial adv = 6 dB ∆SNR loss re n.h. = -9 dB

60 Summary of benefit versus HL 40 dB A 60 dB A 80 dB A Background noise level

61 Why don’t directional microphones help more in noise? (and adaptive noise reduction)

62 1. Impact of open fittings on directivity DI = 3 dB  1.5 dB DI = 10 dB  5 dB Directional Omni-directional

63 Frequency range of directional mic (mild loss) Effect of dynamic noise reduction on directional mic

64 Effect of aiding at 60 dBA (mild loss) Noise = 60 dBA Speech = 64 dBA

65 Noise = 80 dBA Speech = 76 dBA Effect of aiding at 80 dBA (mild loss)

66 2.Impact of reverberation on directivity (and vice versa) Direct Reverberant Total

67 Direct Reverberant Total 2.Impact of reverberation on directivity (and vice versa)

68 Benefit of directional microphones Benefit affected by: –Directivity pattern of microphone –Distance and direction of talker and noise sources –Acoustics of the room –Frequency range over which the hearing aid is directional –Frequency range over which the wearable has usable hearing –Nothing else (OK, Measurement error!!)

69 Conclusion of acoustic analysis 1.People with mild loss need help in noisy places 2.Hearing aids increase the speech information available mostly in quiet places! 3.Mics directional only where there is gain  high frequencies and lower levels  Where audibility is limited by threshold, not noise

70 So, objective benefit questionable, and increasing with degree of loss, but ……. What do hearing aid users say ?

71 Experimental evaluation of self- reported benefit 400 clients sampled from national database –41,521 new clients fitted Feb to Sept, 2004 Audiometric and other details obtained from clients’ files Questionnaire sent to clients 5 to 12 months after fitting –International Outcome Inventory for Hearing Aids –Plus 6 purpose-designed questions Non-responders followed up by phone or additional mail to get a high response rate (effectively 86%)

72 Hearing loss distribution Sample distribution Population distribution

73 Usage of hearing aids

74 Factor analysis of questionnaire Factor Loadings Factor 1Factor 2Factor 3 Q1: want aids Q2: difficulty unaided Q3: use Q4: benefit Q5: residual difficulty Q6: Worth it Q7: Residual handicap Q8: Bother to others Q9: Quality of life Q10: Replace them Q11: Face vision Q12: paper vision Proportion of variance Composite benefitComposite difficultyVision International Outcomes Inventory for Hearing Aids

75 Effect of hearing loss on benefit

76 If hearing loss does not determine benefit, then what does?

77 W ishes A nd N eeds T ool 1.How strongly did you want to get hearing aids?  Wanted it very much  Wanted it quite a lot  Wanted it moderately  Wanted it slightly  Did not want it 2.Overall how much difficulty do you have hearing when you are not wearing your hearing aids?  Very much difficulty  Quite a lot of difficulty  Moderate difficulty  Slight difficulty  No difficulty

78 Difficulty hearing unaided and wish to get hearing aids Unaided difficulty related to wish to get hearing aids Want hearing aids Very much Not at all

79 Need increases with hearing loss

80 Benefit versus need strength

81 Why don’t more people with mild hearing loss even try hearing aids?

82 Factors affecting benefit experienced (and hence the reports of others) Degree of pure-tone loss Self-reported disability and handicap Acceptable Noise Level Stigma / cosmetic concern Manipulation and management Age Tinnitus Personality ….

83 Personality People more likely to acquire hearing aids are: –Open –Non-obsessive –Non-neurotic –Internal locus of control People more likely to report benefit are: –Extroverted –Agreeable

84 Health Belief Model People act rationally, in their best interests, based on their beliefs Weighing up of beliefs for and against a health decision What are the disadvantages of the solution? Do I have a problem? Is it serious enough for me to want to remove it? Is there a solution that works? AdvantagesDisadvantages “My hearing loss is not bad enough to need them” (Kochkin, 1993)

85 Motivation comes from …. Acknowledge loss Experience difficulty Experience handicap Self-image Expect benefit Expect to manage them $ Cost OK Try them

86 Health belief model Hearing loss Cost Difficulties experienced: frequency, severity Self- image Ability to manage Hearing aid effectiveness External image Incon- venience

87 Health belief model Hearing loss Cost Difficulties experienced: frequency, severity Self- image Ability to manage Hearing aid effectiveness External image Inconven -ience

88 Health belief model Hearing loss Cost Difficulties experienced: frequency, severity Self- image Ability to manage Hearing aid effectiveness External image Inconven -ience

89 How can the balance of benefits to disadvantages be improved?

90 Improving advantages and removing disadvantages Problem 1Solution 1 Problem 2Solution 2 Problem 3Solution 3 WDRC Slim-tube, miniaturization Feedback cancellation Low-level expansion Re-chargeable batteries Auto telecoil Frequency lowering Bandwidth extension Trainable responses Adaptive noise reduction Transient noise reduction Directional microphones Cost Working better in noise

91 Speech intelligibility in noise

92 Binaural-Processing Super-directional Microphone (Mejia et al., 2007) W3W3 W4W4 ∑ ∑ R out K Rear- directional array Masking threshold Cross-fading process Outputs with spatial reconstruction HRTF L HRTF R Z -d d = 3 ms delay (Precedence effect) DOA- reconstruction Q1Q1 Q2Q2 Q3Q3 Q4Q4 ∑ Binaural beamformer Main direction al signal W1W1 W2W2 ∑ ∑ L out K Subsidiary signal

93 Super-directional microphones

94 Speech reception threshold in noise Reverberant room: crit dist = 0.4m, radius = 1 m Mejia and Johnson, unpublished data

95 Listener Hearing Aid Linked binaural hearing aid technology Female talker Male talker Children playing

96 Blind-source separation binaural noise reduction Implication: People with mild or moderate hearing loss were not making much use of spatial cues. n.h. benefit from re-insertion of spatial cues h.i. gain most from directivity

97 Effect of super-directivity (mild loss) Super-directional mic not directional at all over a broader and broader range as noise levels rise Conditions: DI = 6 dB when REIG > 3 dB n.h. spatial adv = 6 dB ∆SNR re n.h. = -3.7 dB

98 So super-directivity alone is no use ……..

99 What if we could achieve directivity at low frequencies?

100 Effect of low-frequency directivity (mild loss) Now directional over entire frequency range in noisy places Conditions: DI = 3 dB when REIG ≥ 0 dB n.h. spatial adv = 6 dB ∆SNR re n.h. = -3.7 dB

101 Occlusion with closed molds Vent or leak transmission in

102 Active Occlusion Reduction Hear Aid C Σ B A + -

103 Active occlusion reduction Mejia, Dillon, & Fisher (2008)

104 In combination? Active occlusion reduction (closed mold) Super- directivity = ?+

105 Low-frequency super-directivity (mild loss) Super-directivity over entire frequency range  super-normal hearing Conditions: DI = 6 dB when REIG ≥ 0 dB n.h. spatial adv = 6 dB ∆SNR re n.h. = -3.7 dB

106 Low-frequency super-directivity (mild-moderate loss) Super-normal hearing for the median hearing aid wearer Conditions: DI = 6 dB when REIG ≥ 0 dB n.h. spatial adv = 6 dB ∆SNR re n.h. = -5.1 dB

107 Low-frequency super-directivity (moderate loss, 4FA = 49.8 dB HL) Super-normal hearing in very noisy places for even a moderate-severe loss Conditions: DI = 6 dB when REIG ≥ 0 dB n.h. spatial adv = 6 dB ∆SNR re n.h. = -6.5 dB

108 Adaptive noise reduction Gain dependent on SNR correct in principle, but room for improvement: –Gain reduction can reduce directional mic effectiveness –No point in reducing noise below threshold –Gain increase where SNR is best is just as important

109 Cost Jump to summary

110 Self-fitting hearing aid Audiometer NAL-NL2 Prescription Formula Real-ear to coupler difference Adjust Hearing Aid Automatic Developing countries: 1 audiologist per 500,000 people, to 1 per 6,000,000 Australia, USA: 1 audiologist per 10,000 people Plus trainability

111 Automatic versus manual audiometry 1 kHz

112 Test-retest standard deviations Manual audiometry (5 dB Hughson-Westlake) Automatic audiometry (2 dB final step size) NAL- NL2 RECD Adjust Auto Aud

113 Real-Ear to Dial Difference: Inter-subject standard deviations

114 Insert Saunders & Morgan Valente et al Hawkins et al Supra-aural Valente et al Hawkins etal

115 Trainable Hearing Aids CR Gain CT

116 In summary…

117 In summary very not very many, including spatial hearing loss yes, in noise only in quiet places ….. expected benefit too small re need closed-ear, binaural processing How prevalent is mild hearing loss? How common is hearing aid use amongst those with mild hearing loss? What are the characteristics of mild hearing loss? Is mild hearing loss a problem to people? Do hearing aids help people with mild hearing loss? Why don’t more people with mild hearing loss even try hearing aids? How can hearing aids provide greater benefit where it is most needed?

118 Messages for …. Public health authorities: Increase hearing awareness (prevention, rehabilitation) Increase hearing screening opportunities

119 Messages for …. Clinicians: Discern primary reasons why unmotivated clients are unmotivated Provide information to change unrealistic beliefs Understand and diagnose the fundamental problem that clients are presenting with SRT loss

120 Messages for …. Researchers: Better understanding of the components and causes of SNR loss Prescription procedures for adaptive noise suppression Time constants Relationship with thresholds Relationship with noise spectrum and level

121 Messages for …. Manufacturers: Achieve better performance in noise  Binaural processing  Closed fittings  Wireless  Smarter adaptive noise suppression

122 Hearing aids of the future Convergence: hearing aid/enhancer, phone interface, hearing protector, computer interface (in and out), music player, GPS interface  ?

123 Thanks for listening For the slides from this talk..…

124 Amplification and directivity 50 dBA80 dBA Unaided Aided

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