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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.