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The Effects of Hearing Loss on Binaural Function€¦ · spatial release in speech-on-speech...
Transcript of The Effects of Hearing Loss on Binaural Function€¦ · spatial release in speech-on-speech...
•Outline
Whatarethemajoradvantagesoftwoears?
Howdotheleftandrightsignalsdiffer?Howdoweusethisinformationphysiologically?
Howwellcanweexploitourtwoearsforimportanttasks?LocalizationofsoundsourcesAttendingtosourceofinterestincomplexsituations
Effectsofhearingimpairmentinbinauralprocessing...Interauralparametersensitivityandspeechwithspeechmaskers.(astudybyNathanSpencerinmylab).
Whatlimitsperformancewithimpairments/aids/implants?
Whatarethemajoradvantagesoftwoears?
Redundancy
Localizationofsources
Identifyingroomcharacteristics(size,shape,wallreflectivity,and???)
TheCocktailPartyEffect…Renoir's“LuncheonoftheBoatingParty”
•LocalizationCues:
•ITD:fareardelayed•ILD:farearattenuated•SpectralShapes
Differentsignalsatthetwoears
InterauralTimeDelay(ITD)•versusazimuthθ
•DurlachandColburn, 1978
•InterauralLevelDifference(ILD)•ILDversusazimuthfortwofrequencies•Measurementsandspherecalculations
SpectralShapeInformationasalocalizationcue
Outer Ear (beige), Middle Ear (pink), Inner Ear (Blue, cochlea)
•
lConsiderstimuluscodingandbinauralprocessinginphysiologicalstructures.
lQuickreviewofperipheralphysiology
lAuditoryNerveResponsesandTimingInformation
lSuperiorOlivaryNucleicompareleftandrightresponseswithsensitivitytoITDorILD
PhysiologicalMechanisms
Middle Ear bones
Cochlear spiral
Vestibular and Auditory Nerves
Semicircular Canals
Stapedius muscle attaches to third bone (stapes) and contracts to decrease transmission
May respond in anticipation of loud sounds
RecordingsfromthreeindividualauditorynervefiberswithNOACOUSTICSTIMULUS
•Primary Auditory Nerve Patterns (Kiang, 1965)
•Note the stochastic nature of the response
Rate-intensityfunctionforauditorynervefiber
AuditoryNerveTuningCurves:Levelrequiredfordetectableresponse
Histogramsofresponsestotonesatvariouslevels
Notethathistogramsherecovertwoperiodsofthetonalstimulus
Synchronizationtotonecycles
•JeffressmodelofITDprocessing
•Howdoprocessthistiminginformationtocomparerightandlefttimings
•JeffresspostulatedCoincidenceDetectorNetworkin1948.
•Internaldelaysthataredifferentforeachcellinanarray
•Fixedtimedelayoninputpatternswouldexcitecompensatingdelaycellmoststrongly
•Coincidence Network of Jeffress (1948)
ITD-sensitive neuron in MSO
•MechanismsofITDProcessing
•CodingoftimestructuretoneuralpatternlPrimary auditory nerve coding
•Maintenance/sharpening of temporal structurelSharpening in cochlear nucleus (Bushy Cells of CN)
•Sensitivity to delays of left and right inputslSingle neuron processing in MSO
•Preservation to higher neural levelslMaintenance of “spatial code” for ITD
From Stern and Trahiotis, 1997
Binaural Display: (f,τ)-plane
Narrowband Cross-correlation function for each f
Internal delay limiting function
Resulting distribution of activityITD from ridge
•Interaurallevel(ILD)representation
•LSOneurons(ILDandonset-ITDsensitive)
•Excitatoryinputfromipsilateralside
•Inhibitoryinputfromcontralateralside
•ArrayofILDprocessorsversusfrequency
•DiraniehandColburn,1994•(MODEL)
•LSONeuronandILDsensitivity
•ILD,farrayofLSOneurons
•LSOneuronsareeachILDsensitive
•LSOneuronsaretunedinfrequency(likeauditorynervefibersandMSOcells)
•ProvideinformationaboutILDforeachfrequencyband
•Maybeparticularlyimportantinreverberantenvironments(Hartmann,1999)
InterauralDifference(ITDorILD)ResolutionforHumanSubjects
•Howsmallatimedelaybetweentheearsisreliablydetectablebyahumanlistener?
•CalledaJust-NoticeableDifferenceinITDorILD
•Bestlistenerscandobetterthan10µs −− on the order of ten millionths of a second!
•Best listeners for ILD do about 0.5 decibels
InterauralDifferenceSensitivityversusfrequency
EnvelopecarriesITDatHF
• Temporalsynchronizationtotimingfallsoffathighfrequencies…
• MinimalsensitivitytofinestructureITDaboveabout1500Hzinhumans
• Buthighfrequenciescarryinterauraltiminginformationinsynchronizationtotheenvelopes.Thisisafactorinbinauralperformancebutitiscomplicated.
Envelopeonnoisebandprovidestimingcues
Neuralsynchronizationtotheenvelope(blackcurvewithfrequenciesrelatedtobandwidth)
Nosynchronizationtothefinestructure(i.e.,tothecarrier)athighfrequencies
Howdowehandlethecocktailparty?
• Combinedstimulimixedtogetherineachfrequencyband
• Wewanttousetheinternaldistributionsoverfrequencyandinterauralparameters…maybebasedoninterauraltimeandlevelormayinvolveprocessed,position-basedinformation
• Thesedisplayschangeovertimeasdifferentstimulifromdifferentdirectionsdominate.
• Thisisacomplexchallenge!
Sortingitallout
• Theinformationhastobethere.• Weneedtoignoredistractingsources
– Evidencethatmusicianscandothisbetter– Practicemakesusbetterinanycase– Calledinformationalmaskingversus“energetic”
• Weneedtoexploittheinterauraldifferencesaswellasthedynamictemporalvariations
• Weneedtouseourknowledgeofthesignals
InterauralSensitivitywithHearingLoss(NathanSpencerExperiments)
• Primaryinterestwaseffectsofhearingimpairmentsonbinauralprocessing.
• Measuredinteraural discriminationaswellasspatialreleaseinspeech-on-speechmasking.
• Hypothesizedthatinteraural discriminationability[just-noticeabledifferences(JNDs)ininteraural time,level,andcorrelation]wouldco-varywithspatialseparationbenefits.
NathanSpencerSubjects
• Tenyoungnormal-hearingsubjects,aged20-29
• Tenyounghearing-impairedsubjects.• HI1-HI8,HI10,HI11;aged19-38
• Oneolderhearing-impairedsubject• HI9aged70
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AudiogramssymmetricinallcasesexceptforinHI10,anauthorinthiswork.
Interauraldifferencesensitivitytasks• Stimuli1/3octave,narrow-bandnoises,centeredateitherlowfrequency(500Hz)orhighfrequency(2kHzor4kHz).
• Measuredjust-noticeabledifferences(JNDs),relativetodioticreference(waveformssameinbothears)
§ Interauraltimedifference(ITD)discrimination§ Interauralleveldifference(ILD)discrimination§ Interauralcorrelationdifference(ICC)discrimination
Measuringinterauraldifferencesensitivitythresholds
• Acquiredadaptivetracksto(Levitt,1971)70.7%correct
• Keptmeasuringperformanceinalltasks,overmultipledays
• Calculatedthresholdsanderrorbarsbasedonlasttwelveadaptivetracks
ITDsensitivitymeasurements
• Ininterval2orinterval3,waveformwasdelayedinoneear,relativetoother…creatinganoff-centerimageinonlyoneinterval
• Presentedfourintervals
• Subjectaskedtoidentifywhichinterval(2or3)wasdifferent
• Providedwithfeedback
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Increasingaveragehearingloss
WilcoxonMedianTest…
p>0.05
ILDThresholds(Notelogscale)
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WilcoxonMedianTest…
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HearinglossasafunctionofinterauraldifferencesensitivitythresholdsforHI
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• Nocorrelationsfoundforeitherofthesubjectgroups,foranyinterauraldifferencesensitivitytask
• LackofcorrelationfoundforHIgroupinITDat500Hz
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r²=.84 r²=.25
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IDJNDmeasurementsweregenerallycorrelatedbetweenlowandhighfrequencies,consideredacrosssubjects
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Previousstudies:individualdifferencesininter-auraldifferencesensitivity,notinmonaurallevelsensitivity
• Four,highlytrainedNormal-Hearinglistenersat500Hz(Koehnke etal.1986)…
MONAURALdiscrimination
INTERAURALdiscrimination
InterauralDiscriminationConclusions
• Largeinter-subjectvariability
• Interauraldifferencesensitivitythresholdsdidnotcorrelatewithhearingloss
• ITDandILDthresholdshighlycorrelatedamongbothNHandHIsubjectgroups
• Consistentwithmyseeing“remarkablesubjects”whowereexcellentinbinauraltaskswithseverehearingloss
The famous psychologist George A.Miller once wrote:
"It is said that the best place to hide aleaf is in the forest, and presumably thebest place to hide a voice is among othervoices" (p. 118).
Miller,G.A.(1947) "Themaskingofspeech,"Psychol.Bulletin,44,105-129
Understanding speech in competition with other speechcan be challenging.
NowturntotheCocktailPartyProblem
•E.ColinCherry’s1953summary:
•“Howdowerecognizewhatonepersonissayingwhenothersarespeakingatthesametime(the‘cocktailpartyproblem')?”
•Factors:lVoices from different directionslLip-reading, gestures, and the likelDifferent speaking voices, pitches, speeds, …lAccents differinglTransition-probabilities (subject matter, voice dynamics, syntax, …)
ObtainingSRTs
• UsedproceduresdevelopedbyCarr(2010)(nowCarrLevy)• Adaptivealgorithmusedtodeterminethetarget/masker(T/M)
ratio(dB)for50%correct§ Maskerlevelsfixed
§ NormalhearingEachmaskersetto~45dBaboveSRTinquiet(65dBSPL)
§ HearingimpairedEachmaskerset~25dBaboveSRTinquietinHI,whenpossible
§ Targetlevelvaried
• ForHI11,discomfortthresholdslimitedmaskerlevel,sotargetcouldbelimitedbyaudibility(lessthan10dBabovequietthreshold,Duquesnoy,1983)
Colocated task
6m
10mDifficultcase,ingeneral…
• Alltalkersinthesameposition• Noseparation-relatedcues
~Infront
Sources~1.5mawayfromhead
Symmetricmaskerscondition
6m
10mModeratelydifficult…
• Interauraldifferences• Nolong-termbetterear
~Infront
~60⁰~60⁰
~1.5m
Anti-symmetricmaskerscondition
Expectedtobeeasierthancolocated…
• Long-termbetterear,contralateraltoearwithdominantmasker
• Interaural timedifferences• Interauralleveldifferences
~60⁰ ~Infront
Sources~1.5mfromhead
Measuredperformancebothright-earbetterandleft-earbetter
Colocated task
6m
10mDifficultcase,ingeneral…
• Alltalkersinthesameposition• Noseparation-relatedcues
~Infront
Sources~1.5mawayfromhead
Colocated SRTs
Limitedbyaudibilityp>0.05
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WilcoxonMedianTest…
Anti-symmetriccondition
Expectedtobeeasierthancolocated…
• Long-termbetterear,contralateraltoearwithdominantmasker
• Interaural timedifferences• Interauralleveldifferences
~60⁰ ~Infront
Sources~1.5mfromhead
Measuredperformancebothright-earbetterandleft-earbetter
Anti-symmetricSRTs
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†p<0.05
• “Spatialreleasefrommasking”
• Individualdifferencesareevident
WilcoxonMedianTest…
†
• Monauralbenefit = Colocated – separatedmonaural
Determiningbenefitsofspatialseparation
• Binauralbenefit=Totalbenefit– monauralbenefit
• Totalbenefit=colocated - spatiallyseparated
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Largemonauralbenefit
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r2=.55
ILD500ILD4k
ITD500ITD4k
r2 shownintableRedmeansp<0.05
BinauralBenefitr2 <0.2r2 =0.67
r2=0.51r2 =0.39
Anti-symmetricbinauralbenefitasafunctionofinterauraldifferencesensitivity
NH
BinauralBenefitr2 <.2r2 <.2
r2 <.2r2 N/A
BinauralBenefitN=8r2 =.53N=6r2= 0.64
N=8 0.54N=4 r2 N/A
HI1-8(<70dBHL)HI1-10
Correlationformost interauraldifferencesensitivitythresholds
Correlationfornointerauraldifferencesensitivitythresholds
Correlationforsomeinterauraldifferencesensitivitythresholds
Symmetrictask
6m
10mModeratelydifficult…
• Interauraldifferences• Nolong-termbetterear
~Infront
~60⁰~60⁰
~1.5m
Symmetricbinauralbenefit
Highinter-subjectvariabilityamongeachsubjectgroup
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Symmetricbinauralbenefit
• Binauralbenefitdidnotcorrelatewithhearinglossineithergroup
• Binauralbenefitdidnotcorrelatewithinterauraldifferencesensitivitythresholdsineithergroups
DataConclusions
• Hearinglossakeyfactorinthebinauralbenefitfortheanti-symmetricconditionbutnotforthesymmetriccondition
• Inmostcases,hearing-impairedlistenersbenefitedfrombinaurallistening§ Binauralbenefitsmostlypositiveforanti-symmetric condition§ BinauralbenefitswerealwayspositiveforHIinthesymmetric condition
• Intheanti-symmetriccondition,binauralbenefitwascorrelatedwithsomeinterauraldifferencesensitivitythresholdsforbothnormal-hearingandsubsetofhearing-impairedlisteners
§ Inthesymmetriccondition,binauralbenefitnotcorrelatedwithinterauraldifferencesensitivitythresholds
Timewindowprocessingfactor?
• Inthesymmetriccase,withspeechmaskers,listenersbenefitfromselectivelylisteninginoptimaldirection(and/ortothebetterear)differentlyindifferenttimeintervals
• Thisfactorisdistinctfrominterauralresolutionfactorsandfromattenuationfactors
•Speech Spectrogram
lTime(about3.5seconds)
lFrequency (kHz)
EffectofECwindowlengthonSRT(1xJitter)
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Inconsistentbetter-ear
OverallConclusionsforthisstudy
• Binauralbenefitinanti-symmetricconditionforHIgroupdecreaseswithhearingloss
• Interauraldifferencesensitivityakeyfactorforbinauralbenefitforanti-symmetricspeechcondition§ Correlationswereobservedfornormalhearinggroupandfor
hearing-impairedsubgroupwithless-than-severeaveragehearingloss
§ Modelpredictionsshowlargeeffectofjitterstandarddeviation
• Interauraldifferencesensitivityandhearinglosseachunrelatedtobinauralbenefitforsymmetriccondition§ Neitherinterauraldifferencesensitivitynorhearinglosscorrelated
withbinauralbenefitinthesymmetriccondition§ Modelingresultsshowinfluenceofprocessingwindowduration§ Suggestindependentestimationofprocessingwindowlength
Takehomemessage?
• Theprocessinginmultiplespeechinterferencesituationsisverycomplex– Dependsonlocations,natureofsources,positionsofmaskers,individualabilitytousethemultiplecues,andpossiblyontemporalwindowfactors.
• Neithertheaudiogramnorabilitiestodosimplediscriminationtasksarepredictorsofabilitiesincomplexenvironments
• Teststobedonewithhearingaidsincomplexenvironmentsseemimportanttodevelop.
Ongoingworkonthistopic(withTheoGoverts atVUMC)
• Attempttocharacterizedifficultenvironments– Recording(binaurally)difficultenvironmentsasreportedbylistenerswithhearingimpairments
• Analysisofrecordingsandcomparisonswithsubjectiveimpressions
• Worktodevelopaspeech-in-complex-environmentstestthatcouldbeusedtoevaluatehearingaidsintheclinic.
Physical Acoustics
L(t)
R(t)
Current Model of Sources and Environment
ITD,f array
ILD,f array
freq spectra
ITD,f array
ILD,f array
freq spectra
Compare
Actual to
Hypothesis
Update Mechanism
Peripheral Physiology
Listener’s Learned Transformations
Non-auditory inputs
Real Sources in the real Environment
Fast (Add/Delete/Move Source)
Slow (Pinna)
Internal Representations
ColburnandKulkarni(2005)
StableWorldModel
Acknowledgements
• IRChearing-aidcompanyconsortium
• NationalInstitutesofHealthGrantsupport:– NIDCDR01DC00100
• ManyColleagues,especiallyGeraldKidd,TheoGoverts,SuzanneCarr Levy,NathanSpencer
TheEnd!!