Proceedings Fonetik 2009 - Institutionen för lingvistik

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Proceedings, FONETIK 2009, Dept. of Linguistics, Stockholm UniversityDevelopment of self-voice recognition in childrenSofia StrömbergssonDepartment of Speech, Music and Hearing, School of Computer Science and Communication, KTH,StockholmAbstractThe ability to recognize the recorded voice asone’s own was explored in two groups of children,one aged 4-5 and the other aged 7-8. Thetask for the children was to identify which oneof four voice samples represented their ownvoice. The results indicate that 4 to 5 year-oldchildren perform as well as 7 to 8 year-oldchildren when identifying their own recordedvoice. Moreover, a time span of 1-2 weeks betweenrecording and identification does not affectthe younger children’s performance, whilethe older children perform significantly worseafter this time span. Implications for the use ofrecordings in speech and language therapy arediscussed.IntroductionTo many people, the recorded voice oftensounds unfamiliar. We are used to hearing ourvoice through air and bone conduction simultaneouslyas we speak, and as the recordedspeech lacks the bone conduction filtering, itsacoustic properties are different from what weare used to (Maurer & Landis, 1990). But eventhough people recognize that the recordedvoice sounds different from the voice as wenormally hear it, people most often still recognizethe recording as their own voice. In a recentstudy on brain hemisphere lateralization ofself-voice recognition in adult subjects (Rosa etal, 2008), a mean accuracy of 95% showed thatadults rarely mistake their own recorded voicefor someone else’s voice.Although there have been a few studies onadult’s perception of their own recorded voice,children’s self-perception of their recordedvoices is relatively unexplored. Some studieshave been made of children’s ability to recognizeother familiar and unfamiliar voices. Forexample, it has been reported that children’sability to recognize previously unfamiliarvoices improves with age, and does not approachadult performance levels until the age of10 (Mann et al, 1979). Studies of children’sability to identify familiar voices have revealedthat children as young as three years old performwell above chance, and that this abilityalso improves with age (Bartholomeus, 1973;Spence et al, 2002). However, the variabilityamong the children is large. These reports suggestthat there is a developmental aspect to theability to recognize or identify recorded voices,and that there might be a difference in howchildren perform on speaker identification taskswhen compared to adults.Shuster (1998) presented a study where childrenand adolescents (age 7-14) with deviantspeech production of /r/ were recorded whenpronouncing words containing /r/. The recordingswere then edited so that the /r/sounded correct. A recording in the listeningscript prepared for a particular child could thusbe either an original recording or a “corrected”recording, spoken either by the child himself/herselfor another speaker. The task for thechildren was to judge both the correctness ofthe /r/ and the identity of the speaker. One ofthe findings in this study was that the childrenhad difficulty identifying the speaker as himself/herselfwhen hearing a “corrected” versionof one of their own recordings. The authorspeculates that the editing process could haveintroduced or removed something, therebymaking the recording less familiar to thespeaker. Another confounding factor could bethe 1-2 week time span between the recordingand the listening task; this could also havemade the task more difficult than if the childrenhad heard the “corrected” version directly afterthe recording. Unfortunately, no studies of howthe time span between recording and listeningmight affect children’s performance on speakeridentification tasks have been found, and anyeffects caused by this factor remain unclear.Of the few studies that have been done toexplore children’s perception of recordedvoices – of their own recorded voice in particular– many were done over twenty years ago.Since then, there has been a considerable increasein the number of recording devices thatcan potentially be present in children’s environments.This strongly motivates renewed anddeeper exploration into children’s selfperceptionof their recorded voice, and possibledevelopmental changes in this perceptual abil-136
Proceedings, FONETIK 2009, Dept. of Linguistics, Stockholm Universityity. If it is found that children indeed recognizetheir recorded voice as their own, this may haveimportant implications for the use of recordingsin speech and language intervention.PurposeThe purpose of this study is to explore children’sability to recognize recordings of theirown voice as their own, and whether this abilityvaries depending on the age of the child and thetime between the recording and the listening.The research questions are:1. Are children with normal hearing ableto recognize their own recorded voiceas their own, and identify it when presentedtogether with 3 other childvoices?2. Will this ability be affected by the timespan between recording and listening?3. Will the performance be affected by theage of the child?as references. None of the reference childrenwere known to the children in the test groups.Recording/Identification procedureA computer program was used to present thewords in the scripts in random order, and foreach word1. Play a reference voice (adult) that readsa target word, while displaying a picturethat illustrates the word.2. Record the subject’s production of thesame word (with the possibility of listeningto the recording and re-recordinguntil both child and experimenter aresatisfied).3. Play the subject’s production and 3 referencechildren’s productions of thesame word, in random order, letting thesubject select one of these as his/herown. (See Figure 1.)It is hypothesized that the older children willperform better than the younger children, andthat both age groups will perform better whenlistening immediately after the recording thanwhen listening 1-2 weeks after the recording.MethodParticipants45 children with Swedish as their mothertongue, and with no known hearing problemsand with no previous history of speech and languageproblems or therapy were invited to participate.The children were divided into two agegroups, with 27 children aged 4-5 years (rangingfrom 4;3 to 5;11, mean age 5;3) in theyounger group and 18 children aged 7-8 years(ranging from 7;3 to 8;9, mean age 8;0) in theolder group. Only children whose parents didnot know of or suspect any hearing or languageproblems in the child were invited. All childrenwere recruited from pre-schools in Stockholm.MaterialA recording script of 24 words was constructed(see Appendix). The words in the script all beganwith /tV/ or /kV/, and all had primary stresson the first syllable.Three 6-year old children (two girls and oneboy, included by the same criteria as the childrenparticipating in the study) were recordedFigure 1: The listening/identification setup.In both test sessions, the children were fittedwith a headset and the experimenter with headphonesto supervise the recordings. The childrenwere instructed to select the character theybelieved represented their own voice by pointingat the screen; the actual selection was managedby the experimenter by mouse clicking.The children were given two introductory trainingitems, to assure understanding of the task.In the first test session, the children performedboth the recording and the voice identificationtask, i.e. step 1-3. For the recordings,all children were instructed to speak with theirnormal voice, and utterances were re-recordeduntil both child and experimenter were satisfied.In the second test session, after a period of1-2 weeks, the children performed only theidentification task, i.e. step 3. Apart from generalencouragement, the experimenter provided137
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Department of LinguisticsPhonetics
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