Download Real-time noise reduction system enhances auditory word recall

Real-timenoisereductionsystemenhancesauditorywordrecallperformanceinnoise
ElaineH.N.Ng1,ThomasLunner1,2,andJerkerRönnberg1
1LinnaeusCentreHEAD,SwedishInstituteforDisabilityResearch,DepartmentofBehavioural SciencesandLearning,LinköpingUniversity,Sweden
2EriksholmResearchCentre,Oticon A/S,Snekkersten,Denmark
Testconditions
Noiseimpairsspeechunderstandingandhasanegativeimpacton
rememberingheardspeech.Ngetal.(2013,2015)demonstrated
that,usingtheSentence-finalWordIdentificationandRecall(SWIR)
test,ahearingaidsignalprocessingalgorithmalleviatedthenegative
impactandimprovedmemoryforspeechheardinnoise.Inthese
twostudies,auditorystimuliwerepre-processedoffline,simulating
possiblereal-timehearingaidsignalprocessing.
Methods
Participants
Twenty-sixexperiencedhearingaidusersof38to69yearsofage
(mean=63.5,SD=6.5)withsymmetricalsensorineuralhearingloss
of37to66dBHL(mean=49.1,SD=7.0)weretested.Allwere
nativeSwedishspeakers.
Sentence-finalWordidentificationandRecalltest(SWIR)
Allparticipantslistenedto40listsofsentences,whichareasubset
ofSwedishHINTsentences(Hällgrenetal.,2006).Eachlistcontained
7sentences.Thetaskswereto1)repeatthefinalwordofeach
sentence,and2)recallall7finalwordswhentheendofalistwas
reached.Anexamplesentencelistisshownhere:
Serial position
Pappa ska laga min fåtölj
Tanten handlar en gång i veckan
Rektorn tog fram kastrullen
Farmor åker till golfbanan
Golvet täcktes av en vit matta
Frukten packades i sex lådor
Plånboken låg kvar på isen
Primacy
Procedure
• Participantswerefittedwithapairofexperimentalbehind-the-ear
hearingaidsimplementedwiththenoisereductionsystem.Hearing
aidamplificationswereprescribedbasedontheiraudiograms.
• Theywerethenseatedinananechoicroomequippedwithfive
loudspeakersonacirclewithradiusof1meterandthelistenerin
thecenter.Speechstimuliwerepresentedfromthefront(0°).Four
tracksofone-talkerbabblewerepresentedfromloudspeakers
placedat90°,135°,225° and270°.
Estimation of thepresentationlevels
1) SNRyielding80%speechrecognitionin4-talkerbabblewas
obtainedusingSwedishHINTsentencesforeachparticipant.The
noisereductionsystemwasOFF.
2) Anindividualpsychometricfunctionwasthenplottedusingthe
datapointsfromthefirststep.
3) Foreachparticipant,SNRspredicting70%(meanacross
participants=1.8dBSNR,SD=2.2)and95%speechrecognition
(meanacrossparticipants=4.0dBSNR,SD=2.4)wereestimated
fromthispsychometricfunction.
Results
ResultsareshowninTable1.Recallperformanceineachtestcondition
wasanalyzedintermsofseriallistposition.AnANOVAwiththree
within-subjectfactors(presentationlevel,noisereductionandserial
position)wasperformed.
Thethree-wayinteraction(presentationlevelxnoisereductionxserial
position;seeFigure1)wasstatisticallysignificant,F(2,50)=3.3,p <
0.05.
100
NR OFF
80
NR ON
60
40
20
0
Primacy
Asymptote
Recency
Primacy
Asymptote
95%
70%
Recency
Figure 1. Significant 3-way
interaction between
presentation level, noise
reduction and serial
position. Error bars
represent standard errors.
Discussions
• Thisisthefirststudyshowingthatareal-timenoisereduction
algorithmsignificantlyimprovesmemoryrecallforspeechheardin
noise.
• At95%speechintelligibility:Whenspeechishighlyintelligible,
noisereductionimprovesmemoryrecallacrossallserialpositions.
Thissuggeststhatnoisereductionalleviatestheadverseeffectof
noiseonmemoryforheardspeech byfreeingupcognitive
resources.
• At70%speechintelligibility:Thebenefitwasgreatestinprimacy
positionwhenlisteningsituationbecomeschallenging.Better
Therewerethreesignificantmaineffects:
performanceintheprimacypositioncorrespondstobetter
• Presentationlevel(95%>70%),F(1,25)=11.0,p <0.01
encodingofwordsintolong-termmemory,whichisanecologically
• Noisereduction(ON>OFF),F(1,25)=15.2,p <0.01
importantaspectofspeechunderstandingunderadverse
• Serialposition(recency >primacy>asymptote),F(2,50)=56.3,
conditions.
p <0.001
70%
95%
NR OFF
52.5% (16.2%)
56.6% (16.1%)
NR ON
57.1% (17.2%)
60.1% (17.7%)
Asymptote
Recency
Atwo-wayinteraction(presentationlevelxserialposition)was
approachingstatisticalsignificance,F(2,50)=2.5,p =0.087,suggesting
thatrecallperformance,particularlyforwordsintheprimacyposition,
wasbetterat95%speechintelligibilitythanthatat70%.
*
Thepresentstudyaimedto1)measurethebenefitofanoise
reductionsystemimplementedinhearingaidswhenallauditory
stimuliwereprocessedinreal-time;and2)comparethebenefitin
termsofmemoryperformanceatdifferentpresentationlevels(SNRs
predicting95%and70%speechintelligibilityinnoise).Theselevels
werechosenbecausetheauditorystimuliwouldbepresentedin
positiveSNRs,atwhicheverydaycommunication(ecological
listeningconditions)takesplace(Lunner etal.,2016;Smeds etal.,
2015).
Fourtestconditions(2x2design);5listspercondition
- Presentationlevel:
IndividualizedSNRspredicting70%and95%speechintelligibility
innoise
- Noisereductionsystem:
OpenSound Navigator (LeGoffetal.,2016): NRON,NROFF
Recall performance (%)
Introduction
References
Hällgren,M.,Larsby,B.,&Arlinger,S.(2006).ASwedishversionoftheHearingInNoiseTest(HINT)formeasurementofspeechrecognition.Int JAudiol, 45(4),227–237.
LeGoff,N.,Jensen,J,Perdersen,M.S.,Callaway,S.L.(2016),AnintroductiontoOpenSound navigator,Whitepaper,Oticon A/S.
Lunner,T.,Rudner,M.,Rosenbom,T.,Ågren,J.&NgE.H.N.(2016).UsingSpeechRecallinHearingAidFittingandOutcomeEvaluationUnderEcologicalTestConditions,EarHear.
Ng,E.H.N.,Rudner,M.,Lunner,T.,Pedersen,M.S.,&Rönnberg,J. (2013).Effectsofnoiseandworkingmemorycapacityonmemoryprocessingofspeechforhearingaidusers.Int JAudiol,52(7),433-441.
Ng,E.H.N.,Rudner,M.,Lunner,T.,&Rönnberg,J.(2015).Noisereductionimprovesmemoryfortargetlanguagespeechincompetingnativebutnotforeignlanguagespeech.EarHear,36(1),82-91.
Smeds,K.,Wolters,F.,andRung,M.(2015).Estimationofsignal-to-noiseratiosinrealisticsoundscenarios.JAmAcadAudiol,26,183–196.
Acknowledgements
Table 1. Mean recall
performance (and SD) in
each test condition.
TheauthorswouldliketothankNicolasLeGoffandThomasBehrens
fromOticon A/S,Smørum,Denmark,fortheircontributionsofideas
regardingthestudydesign.ThisprojectwasfundedbyOticon A/S.