Proceedings Fonetik 2009 - Institutionen för lingvistik

More documents

Recommendations

Info

Proceedings, FONETIK 2009, Dept. of Linguistics, Stockholm Universitybars used in the equalizers of sound systems:the current amount of variation is indicated bythe number of bars that are lit up in a stack ofbars, and the highest variation over the past twoseconds is indicated by a lingering top bar. Themeter has a short, constant latency of 100ms.The test group and the control group eachconsisted of 7 students of engineering, 4women and 3 men each. The participants wererecruited from English classes at KTH, andwere exchange students from China, in Swedenfor stays of six months to two years. Participants’proficiency in English was judged bymeans of an internal placement test to be at theupper intermediate to advanced level. The participantsspoke a variety of dialects of Chinesebut used Mandarin with each other and for theirstudies in China. They did not speak Swedishand were using English with their teachers andclassmates.Each participant began the study by givingan oral presentation of about five minutes inlength, either for their English classes or for asmaller group of students. Audio recordingswere made of the presentations using a smallclip-on microphone that recorded directly into acomputer. The presentations were also videorecorded,and participants watched the presentationstogether with one of the researchers,who commented on presentation content, deliveryand language. The individualized trainingmaterial for each subject was prepared from theaudio recordings. A set of 10 utterances, eachof about 5-10 seconds in length, was extractedfrom the participants’ speech. The utteranceswere mostly non-consecutive and were chosenon the basis of their potential to provide examplesof contrastive pitch movement within theindividual utterance. The researcher recordedher own (native-American speaking) versionsof them, making an effort to use her voice asexpressively as possible and making more pitchcontrasts than in the original student version.For example, a modeled version of a student’sflat utterance could be represented as: “AndTHIRDly, it will take us a lot of TIME and EFfortto READ each piece of news.”The participants were assigned to the controlor test groups following the preparation oftheir individualized training material. Participantswere ranked in terms of the global pitchvariation in their first presentation, as follows:they were first split into two lists according togender, and each list was ordered according toinitial global pitch variation. Participants wererandomly assigned pair-wise from the list to thecontrol or test group, ensuring gender balanceas well as balance in initial pitch variation.Four participants who joined the study at a laterdate were distributed in the same manner.Participants completed approximately threehours of training in half-hour sessions; someparticipants chose to occasionally have back-tobacksessions of one hour. The training sessionswere spread out over a period of fourweeks. Training took place in a quiet and privateroom at the university language unit, withoutthe presence of the researchers or otheronlookers. For the first four or five sessions,participants listened to and repeated the teacherversions of their own utterances. They were instructedto listen and repeat each of their 10 utterancesbetween 20 and 30 times. Test groupparticipants received the visual feedback describedabove and were encouraged to speak sothat the meter showed a maximum amount ofgreen bars. The control group was able to listento recordings of their production but receivedno other feedback.Upon completion of the repetitions, bothgroups were encouraged to use the system topractice their second oral presentation, whichwas to be on a different topic than the firstpresentation. For this practice, the part of theinterface designated for ‘free speech’ was used.In these sessions, once again the test participantsreceived visual feedback on their production,while control participants were only ableto listen to recordings of their speech. Within48 hours of completing the training, the participantsheld another presentation, this time aboutten minutes in length, for most of them as partof the examination of their English courses.This presentation was audio recorded.ResultsWe measured development in two ways: overthe roughly three hours of training per student,in which case we compared pitch variation inthe first and the second half of the training foreach of the 10 utterances used for practice, andin generalized form, by comparing pitch variationin two presentations, one before and oneafter training. Pitch estimations were extractedusing the same software used to feed the pitchvariation indicator used in training, an incrementalversion of the getF0/RAPT (Talkin,1995) algorithm. Variation was calculated in amanner consistent with Hincks (2005) by calcu-104
Proceedings, FONETIK 2009, Dept. of Linguistics, Stockholm Universitylating the standard deviation over a moving 10second window.In the case of the training data, recordingscontaining noise only or those that were emptywere detected automatically and removed. Foreach of the 10 utterances included in the trainingmaterial, the data were split into a first anda second half, and the recordings from the firsthalf were spliced together to create one continuoussound file, as were the recordings fromthe second half. The averages of the windowedstandard deviation of the first and the secondhalf of training were compared.Average standard deviation in semitones1210864201st presentation 1st half training 2nd half training 2nd presentationFigure 1. Average pitch variation over 10 secondsof speech for the two experimental conditions duringthe 1st presentation, the 1st half of the training,the 2nd half of the training and the 2nd presentation.The test group shows a statistically significanteffect of the feedback they were given.The mean standard deviations for each dataset and each of the two groups are shown inFigure 1. The y-axis displays the mean standarddeviation per moving 10-second frame ofspeech in semitones, and the x-axis the fourpoints of measurement: the first presentation,the first half of training, the second half oftraining, and the second oral presentation. Theexperimental group shows a greater increase inpitch variation across all points of measurementfollowing training. Improvement is most dramaticin the first half of training, where the differencebetween the two groups jumps significantlyfrom nearly no difference to one of morethan 2.5 semitones. The gap between the twogroups narrows somewhat in the production ofthe second presentation.testcontrolThe effect of the feedback method (testgroup vs. control group) was analyzed using anANOVA with time of measurement (1st presentation,1st half of training, 2nd half of training,2nd presentation) as a within-subjects factor.The sphericity assumption was met, and themain effect of time of measurement was significant(F = 8.36, p < .0005, η² = 0.45) indicatingthat the speech of the test group receivingvisual feedback increased more in pitchvariation than the control group. Betweensubjecteffect for feedback method was significant(F = 6.74, p =.027, η² = 0.40). The two hypothesesare confirmed by these findings.DiscussionOur results are in line with other research thathas shown that visual feedback on pronunciationis beneficial to learners. The visual channelprovides information about linguistic featuresthat can be difficult for second language learnersto perceive audibly. The first language ofour Chinese participants uses pitch movementto distinguish lexical meaning; these learnerscan therefore experience difficulty in interpretingand producing pitch movement at a discourselevel in English (Pennington & Ellis,2000; Pickering, 2004; Wennerstrom, 1994).Our feedback gave each test participant visualconfirmation when they had stretched the resourcesof their voices beyond their own baselinevalues. It is possible that some participantshad been using other means, particularly intensity,to give focus to their English utterances.The visual feedback rewarded them for usingpitch movement only, and could have been apowerful factor in steering them in the directionof an adapted speaking style. While our datawere not recorded in a way that would allowfor an analysis of the interplay between intensityand pitch as Chinese speakers give focus toEnglish utterances, this would be an interestingarea for further research.Given greater resources in terms of time andpotential participants, it would have been interestingto compare the development of pitchvariation with other kinds of feedback. For example,we could have displayed pitch tracingsof the training utterances to a third group ofparticipants. It has not been an objective of ourstudy, however, to prove that our method is superiorto showing pitch tracings. We simplyfeel that circumventing the contour visualizationprocess allows for the more autonomoususe of speech technology. A natural develop-105
Page 1 and 2:
Department of LinguisticsProceeding
Page 3 and 4:
Proceedings, FONETIK 2009, Dept. of
Page 5 and 6:
Page 7 and 8:
Page 9 and 10:
Page 11 and 12:
Page 13 and 14:
Page 15 and 16:
Page 17 and 18:
Page 19 and 20:
Page 21 and 22:
Page 23 and 24:
Page 25 and 26:
Page 27 and 28:
Page 29 and 30:
Page 31 and 32:
Page 33 and 34:
Page 35 and 36:
Page 37 and 38:
Page 39 and 40:
Page 41 and 42:
Proceedings, FOETIK 2009, Dept. of
Page 43 and 44:
Page 45 and 46:
Page 47 and 48:
Page 49 and 50:
Page 51 and 52:
Page 53 and 54: Proceedings, FONETIK 2009, Dept. of
Page 103: Proceedings, FONETIK 2009, Dept. of
Page 127 and 128: Proceedings, FOETIK 2009, Dept. of
Page 155 and 156:
Page 157 and 158:
Page 159 and 160:
Page 161 and 162:
Page 163 and 164:
Page 165 and 166:
Page 167 and 168:
Page 169 and 170:
Page 171 and 172:
Page 173 and 174:
Page 175 and 176:
Page 177 and 178:
Page 179 and 180:
Page 181 and 182:
Page 183 and 184:
Page 185 and 186:
Page 187 and 188:
Page 189 and 190:
Page 191 and 192:
Page 193 and 194:
Page 195 and 196:
Page 197 and 198:
Page 199 and 200:
Page 201 and 202:
Page 203 and 204:
Page 205 and 206:
Page 207 and 208:
Page 209 and 210:
Page 211 and 212:
Page 213 and 214:
Page 215 and 216:
Page 217 and 218:
Page 219 and 220:
Page 221 and 222:
Page 223 and 224:
Page 225 and 226:
Page 227:
Department of LinguisticsPhonetics
show all

Proceedings Fonetik 2009 - Institutionen för lingvistik

Create successful ePaper yourself

Delete template?

Save as template?