Proceedings Fonetik 2009 - Institutionen för lingvistik

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Proceedings, FONETIK 2009, Dept. of Linguistics, Stockholm UniversityChildren’s vocal behaviour in a pre-school environmentand resulting vocal functionMechtild Tronnier 1 and Anita McAllister 21 Department of Culture and Communication, University of Linköping2 Department of Clinical and Experimental Medicine, University of LinköpingAbstractThis study aims to shed some light onto the relationshipbetween the degree of hoarseness inchildren’s voices observed at different timesduring a day in pre-school and different aspectsof their speech behaviour. Behaviouralaspects include speech activity, phonation time,F0 variation, speech intensity and the relationshipbetween speech intensity and backgroundnoise intensity. The results show that childrenbehave differently and that the same type of behaviourhas a varied effect on the differentchildren. It can be seen from two children withotherwise very similar speech behaviour, thatthe fact that one of them produces speech at ahigher intensity level also brings about an increaseof hoarseness by the end of the day inpre-school. The speech behaviour of the childwith highest degree of hoarseness on the otherhand cannot be observed to be putting an extremeload on the vocal system.IntroductionSpeaking with a loud voice in noisy environmentsin order to making oneself heard demandssome vocal effort and has been shown toharm the voice in the long run.In several studies on vocal demands for differentprofessions it has been shown that preschoolteachers are rather highly affected andthat voice problems are common (Fritzell,1996; Sala, Airo, Olkinuora, Simberg, Ström,Laine, Pentti, & Suonpää 2002; Södersten,Granqvist, Hammarberg & Szabo, 2002). Thisproblem is to a large extent based on the needof the members of this professional group tomake themselves heard over the surroundingnoise, mainly produced by the children present.It is reasonable to assume that children’svoices are equally affected by background noiseas adult voices. As children most of the timecontribute to the noise in a pre-school settingthemselves – rather then other environmentalfactors as traffic etc. – they are exposed to thenoise source even more potently as they arecloser to the noise source. Another factor pointingin the same direction is their shorter bodylength compared to pre-school teachers.In an earlier study by McAllister et al.,(2008, in press), the perceptual evaluation ofpre-school children showed that the girls’voices revealed higher values on breathiness,hyperfunction and roughness by the end of theday, which for the boys was only the case forhyperfunction.In the present study the interest is directedto speech behaviour of children in relation tothe background noise and the affect on the vocalfunction. Diverse acoustic measurementswere carried out for this purpose.The investigation of speech activity is chosento show the individuals’ liveliness in thepre-school context and includes voiced andvoiceless speech segments, even non speechvoiced segments such as laughter, throat clearing,crying etc. In addition, measurements onphonation time were chosen, reflecting the vocalload. It should be noted that in some parts ofspeech intended voicing could fail due to theirregularity of the vocal fold vibrations – thehoarseness of the speaker’s voice. Therefore,both measurements, speech activity and phonationtime were considered important. In a studyon phonation time for different professions,Masuda et al. (1993) showed that the proportionfor pre-school teachers corresponded to20% during working time, which is considereda high level compared to e.g. nurses with a correspondinglevel of 5.3% (Ohlsson, 1988). Havingthese findings in mind, the degree of children’sspeech activity and phonation time andthe consequences for perceived voice quality isan interesting issue.Other factors for the analysis of vocal loadconsist of F0 including F0-variation and speechintensity including intensity variation. A vocaltrauma can be based on using high fundamentalfrequency and high vocal loudness (and hyperfunction,which this study is not focusing on inparticular), as Södersten et al. point out.One further aspect that may increase therisk for voice problems is the need of a speakerto be heard over background noise. Therefore,120
Proceedings, FONETIK 2009, Dept. of Linguistics, Stockholm Universitythe relationship speech intensity/backgroundnoise intensity is investigated. According to theresults of Södersten et al. the subjects speechwas 9.1dB louder than the environmental noise,in an already noisy environment.Material and MethodThe material investigated in the present study ispart of the data gathered for the project Barnoch buller (Children and noise). The project is acooperation between the University ofLinköping and KTH, Stockholm, within the largerBUG project (Barnröstens utveckling ochgenusskillnader; Child Voice Development andGenderDifferences;http://www.speech.kth.se/music/projects/BUG/abstract.html). It consists of the data of selectedrecordings from four five-year-old children, attendingdifferent pre-schools in Linköping.These children were recorded using a binauraltechnique (Granqvist, 2001) three times duringone day at the pre-school: at arriving in themorning (m) and gathering, during lunch (l)and in the afternoon during play time (a). Thebinaural recording technique makes it possibleto extract one audio file containing the child’sspeech activity (1) and one file containing thesurrounding sound (2). Each recording consistedof two parts. First a recording with a controlledcondition was made, where the childrenwere asked to repeat the following phrases threetimes: “En blå bil. En gul bil. En röd bil”. Furthermorespontaneous speech produced duringthe following activities at the pre-school wererecorded for approximately one hour.The recordings of the controlled condition,comprising the phrase repetitions, were used inan earlier study (McAllister et al., in press) toperceptually assess the degree of hoarseness,breathiness, hyperfunction and roughness bythree professional speech pathologists. Assessmentwas carried out by marking the degree ofeach of the four voice qualities plus an optionalparameter on a Visual Analog Scale (VAS).The averaged VAS-ratings by the speechpathologists for the four children regarding thecomprehensive voice quality hoarseness wereused as a selection criterion in the present investigation.The selected children showed differenttendencies regarding the hoarsenessvariation over the day at pre-school (see e.g.Table 1).• child A showed a marked increase ofhoarseness,• child B showed some increase of hoarseness,• child C showed no increase of hoarseness,• child D showed a clear decrease of hoarseness.The development of the children’s voicesover the day was compared to the developmentof several acoustic measures of the recordingsof spontaneous speech, shedding light on thechildren’s speech behaviour and activity andthe use of the voiceThe speech activity of each child duringeach recording session was calculated by settingthe number of obtained intensity counts in relationto the potential counts of the whole recordingaccording to an analysis in PRAAT witha sampling rate of 100Hz (in %).Furthermore phonation time was calculatedby setting the number of obtained F0-measuresin relation to the potential counts of the wholerecording according to an analysis in PRAATwith a sampling rate of 100Hz (in %).An analysis of the fundamental frequencyand the intensity was carried out in PRAAT witha sampling rate of 100Hz for file (1), whichcontains the child’s speech. Intensity measureswere also normalised in comparison to a calibrationtone and with regard to microphone distancefrom the mouth to 15 cm.For both F0- and intensity measurements,the mean value, standard deviation and median(in Hz and dB) was calculated. For the sake ofinterpretation of the results regarding the measurementsof fundamental frequency, additionalF0-measurements of controlled speech obtainedfrom the BUG-material for each child is givenin the results.Concerning the background noise investigation,the intensity was calculated in PRAAT witha sampling rate of 100Hz for file (2). Intensitymeasurements for this channel were normalisedin comparison to a calibration tone.Descriptive statistics for the interpretation ofthe measurements was used. The degree ofhoarseness is not a direct consequence of thespeech behaviour reflected by the acousticmeasurements presented in the same rows inthe tables below, because the recordings of thecontrolled condition were made before the recordingsof spontaneous speech.ResultsIn this section the results of the diverse measurementsare presented. In the tables, the perceptualratings of degree of hoarseness obtainedfrom an earlier study are shown, too. They are,however, not considered any further here but121
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