3What is mild hearing loss? Four-frequency average (500, 1000, 2000, 4000 Hz) hearing loss in better ear between 20 and 40 dB HLSelf-reported disability or handicap within a certain rangeSRT in noise loss of between 3 and 6 dB
12Mild losses for study ~ Minimum loss eligible for government benefits Mild loss (4FA=29 dB)Mild-mod loss (4FA=39 dB)~ Median loss newly fitted in Australia
13Mild losses for study 4FA HL Mild 9 dB Mild-mod 39 dB Moderate 49 dB Mod-Sev dBSevere dB
14How common is hearing aid use amongst those with mild hearing loss?
15Penetration by hearing loss Penetration as a function of hearing lossDavis (1995)Wilson et al (1998)Hartley et al (in Press)Kochkinconsistent
16Aid ownership by hearing loss Blue Mountains Population >55 years Overall Use/Ownership =75% if include all use categoriesOverall Use/Ownership =68% if include all use of more than 1 hr/weekHartley et al (in Press)
17What are the characteristics of mild hearing loss?
18Characteristics of mild loss Threshold elevation √Loss of OHC/OAELoss of frequency resolution – TEN, PTC, FRILoss of temporal (envelope) resolutionLoss of fine temporal informationLoss of spatial processingLoss of SRT in noiseIncreased disability and handicap
26Spatial Processing Disorder NoiseNoiseSpeechSharon CameronNoisePrevious research at NAL has shown that a number of children with suspected APD have difficulty separating sounds that arrive simultaneously at the ears from different locations.Tendency to affect children with history of COM.Deficit likely related to ability to use binaural (ITD; IID) cuesNoise2626
27Listening in Spatialised Noise - Sentences (LiSN-S) Conditions Same voicesDifferent voicesTalker AdvantageSamedirectionLow CueSpatial AdvantageTotal AdvantageDifferentdirectionsHigh CueCameron & Dillon (2009)27
29Spatial Advantage (≡ Spatial Release from Masking) Nth AmericaAustraliaBetterThis graph shows performance on the spatial advantage measure.Spatial advantage is calculated as the difference between the low-cue SRT and SV90 condition.Adult like performance on the spatial advantage measure is achieved earlier than on talker advantage. Children are able to use ITD and IID as well as adults by about 11 years of age.Again, there is no decline in spatial processing ability in older adults.29
30Spatial Advantage Better Control vs. LD: p = 0.983 Control vs. SusCAPD: p < *SusCAPD vs. LD: p = *
32Spatial processing remediation Pre vs. Post (n=9) LC SRT p = 0.158Talker Advantage - p = 0.981HC SRT p =Spatial Advantage - p =Total Advantage - p = 0.001Vertical bars denote 0.95 confidence intervalsF(8, 64)=5.3847, p=.0000332
34Spatial hearing loss in hearing-impaired people: LiSN-S Prescribed Gain Amplifier
35Deficit in SRTn with hearing loss P =Cameron, Glyde & Dillon, unpublished data)
36Cause of deficit in SRTn P =Cameron, Glyde & Dillon, unpublished data)
37Talker advantage deficit versus age Cameron, Glyde & Dillon, unpublished data)
38Binaural processing x x ~ Executive control CAPD ILD ITD CN SO / IC / A1ILDITDxLR~Sensorineuralhearing loss
39Loss 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 lossLoss of Talker cue release from masking of 0.5 dB per 10 years of age
40Loss of SRT in noiseCommonly 1.5 dB increase in SNR per 10 dB of hearing lossSNR = -4 dB1 dB / 10 dB1.8 dB / 10 dBCarter, Zhou & Dillon, unpublished data)
41Should mild hearing loss interfere with speech perception?
42Speech and noise levels SNRSource: Pearsons, Bennett and Fidell (1977)
46Mild losses for studyMild loss (4FA=29 dB)Mild-mod loss (4FA=39 dB)
47Predicted speech intelligibility Greatest problems in noisy places !!
48Predicted variation of SRTn with hearing loss Modified SII model predicts only 0.4 dB loss per 10 dB of hearing lossSpeechlevel
49Modification of SIIAssume normal hearers get 6 dB advantage from spatial separation of speech and noiseAssume 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
54Speech intelligibility (mild loss) Hearing aid “helps” in quiet placesTiny additional benefit from directivityConditions:DI = 3 dB when REIG > 3 dBn.h. spatial adv = 6 dB∆SNR re n.h. = -3.7 dB
55Speech intelligibility (mild-moderate loss) Hearing aid “helps” in quiet placesTiny additional benefit from directivityConditions:DI = 3 dB when REIG > 3 dBn.h. spatial adv = 6 dB∆SNR re n.h. = -5.1 dB
56Speech intelligibility (moderate loss) Conditions:DI = 3 dB when REIG > 3 dBn.h. spatial adv = 6 dB∆SNR re n.h. = -6.5 dB
57Speech intelligibility (moderate-severe loss) Conditions:DI = 3 dB when REIG > 3 dBn.h. spatial adv = 6 dB∆SNR re n.h. = -7.7 dB
58Speech intelligibility (severe loss) Conditions:DI = 3 dB when REIG > 3 dBn.h. spatial adv = 6 dB∆SNR loss re n.h. = -9 dB
59Summary of benefit versus HL Background noise level40 dB A60 dB A80 dB A
60Why don’t directional microphones help more in noise? (and adaptive noise reduction)
611. Impact of open fittings on directivity Omni-directionalDirectionalDI = 3 dB 1.5 dBDI = 10 dB 5 dB
62Frequency range of directional mic (mild loss) Effect of dynamic noise reduction on directional mic50607080
63Effect of aiding at 60 dBA (mild loss) Noise = 60 dBASpeech = 64 dBA
64Effect of aiding at 80 dBA (mild loss) Noise = 80 dBASpeech = 76 dBA
652. Impact of reverberation on directivity (and vice versa) TotalReverberantDirect
66Impact of reverberation on directivity (and vice versa) TotalDirectReverberant
67Benefit of directional microphones Benefit affected by:Directivity pattern of microphoneDistance and direction of talker and noise sourcesAcoustics of the roomFrequency range over which the hearing aid is directionalFrequency range over which the wearable has usable hearingNothing else(OK, Measurement error!!)
68Conclusion of acoustic analysis People with mild loss need help in noisy placesHearing aids increase the speech information available mostly in quiet places!Mics directional only where there is gainhigh frequencies and lower levelsWhere audibility is limited by threshold, not noise
69So, objective benefit questionable, and increasing with degree of loss, but ……. What do hearing aid users say ?
70Experimental evaluation of self-reported benefit 400 clients sampled from national database41,521 new clients fitted Feb to Sept, 2004Audiometric and other details obtained from clients’ filesQuestionnaire sent to clients 5 to 12 months after fittingInternational Outcome Inventory for Hearing AidsPlus 6 purpose-designed questionsNon-responders followed up by phone or additional mail to get a high response rate (effectively 86%)
71Hearing loss distribution Sample distributionOverall Use/Ownership =75% if include all use categoriesOverall Use/Ownership =68% if include all use of more than 1 hr/weekPopulation distribution
75If hearing loss does not determine benefit, then what does?
76Wishes And Needs Tool 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 itOverall 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
77Difficulty hearing unaided and wish to get hearing aids Want hearing aidsVery muchNot at allUnaided difficulty related to wish to get hearing aids
80Why don’t more people with mild hearing loss even try hearing aids?
81Factors affecting benefit experienced (and hence the reports of others) Degree of pure-tone lossSelf-reported disability and handicapAcceptable Noise LevelStigma / cosmetic concernManipulation and managementAgeTinnitusPersonality ….
82Personality People more likely to acquire hearing aids are: OpenNon-obsessiveNon-neuroticInternal locus of controlPeople more likely to report benefit are:ExtrovertedAgreeable
83Health Belief ModelPeople act rationally, in their best interests, based on their beliefsWeighing up of beliefs for and against a health decisionDo I havea problem?Is it seriousenough for me towant to remove it?Is there asolutionthat works?DisadvantagesAdvantagesWhat are thedisadvantagesof the solution?“My hearing loss is not bad enough to need them” (Kochkin, 1993)
84Motivation comes from …. Try themSelf-imageExpect benefitExpect to manage them$ Cost OKAcknowledge lossExperience difficultyExperience handicap
93Speech reception threshold in noise Reverberant room: crit dist = 0 Speech reception threshold in noise Reverberant room: crit dist = 0.4m, radius = 1 mMejia and Johnson, unpublished data
94Linked binaural hearing aid technology FemaletalkerMaletalkerListenerChildrenplayingHearing Aid9494
95Blind-source separation binaural noise reduction h.i.gain most from directivityn.h. benefit from re-insertion of spatial cuesImplication: People with mild or moderate hearing loss were not making much use of spatial cues.
96Effect of super-directivity (mild loss) Super-directional mic not directional at all over a broader and broader range as noise levels riseConditions:DI = 6 dB when REIG > 3 dBn.h. spatial adv = 6 dB∆SNR re n.h. = -3.7 dB
103Active occlusion reduction In combination?Active occlusion reduction(closed mold)Super-directivity+= ?
104Low-frequency super-directivity (mild loss) Super-directivity over entire frequency range super-normal hearingConditions:DI = 6 dB when REIG ≥ 0 dBn.h. spatial adv = 6 dB∆SNR re n.h. = -3.7 dB
105Low-frequency super-directivity (mild-moderate loss) Super-normal hearing for the median hearing aid wearerConditions:DI = 6 dB when REIG ≥ 0 dBn.h. spatial adv = 6 dB∆SNR re n.h. = -5.1 dB
106Low-frequency super-directivity (moderate loss, 4FA = 49.8 dB HL) Super-normal hearing in very noisy places for even a moderate-severe lossConditions:DI = 6 dB when REIG ≥ 0 dBn.h. spatial adv = 6 dB∆SNR re n.h. = -6.5 dB
107Adaptive noise reduction Gain dependent on SNR correct in principle, but room for improvement:Gain reduction can reduce directional mic effectivenessNo point in reducing noise below thresholdGain increase where SNR is best is just as important
109Self-fitting hearing aid AutomaticReal-ear to coupler differenceAdjust Hearing AidNAL-NL2 Prescription FormulaAudiometerPlus trainabilityAustralia, USA: 1 audiologist per 10,000 peopleDeveloping countries: 1 audiologist per 500,000 people, to 1 per 6,000,000
116In summary How prevalent is mild hearing loss? very How common is hearing aid use amongst those with mild hearing loss?not verymany, including spatial hearing lossWhat are the characteristics of mild hearing loss?Is mild hearing loss a problem to people?yes, in noiseDo hearing aids help people with mild hearing loss?only in quiet places….. expected benefit too small re needWhy don’t more people with mild hearing loss even try hearing aids?How can hearing aids provide greater benefit where it is most needed?closed-ear, binaural processing
117Messages for …. Public health authorities: Increase hearing awareness (prevention, rehabilitation)Increase hearing screening opportunities
118Messages for …. Clinicians: Discern primary reasons why unmotivated clients are unmotivatedProvide information to change unrealistic beliefsUnderstand and diagnose the fundamental problem that clients are presenting with SRT loss
119Messages for …. Researchers: Better understanding of the components and causes of SNR lossPrescription procedures for adaptive noise suppressionTime constantsRelationship with thresholdsRelationship with noise spectrum and level
120Messages for …. Manufacturers: Achieve better performance in noise Binaural processing Closed fittings Wireless Smarter adaptive noise suppression
121Hearing aids of the future ?Convergence:hearing aid/enhancer,phone interface,hearing protector,computer interface (in and out),music player,GPS interface
122For the slides from this talk ..… www.nal.gov.au Thanks for listeningFor the slides from this talk ..…
123Amplification and directivity 50 dBA80 dBAUnaidedAssumptions: 3 dB DI for REIG > 5 dB3 dB spatial advantage and -3 dB spatial lossAided