Acoustic coustic Realization and Perception of English Lexical Stress by Mandarin Learners

Transcription

1 Acoustic coustic Realization and Perception of English Lexical Stress by Mandarin Learners Yuwen Lai University of British Columbia University of Kansas Joan Sereno University of Kansas Allard Jongman University of Kansas 1

2 Background Segmental learning Flege 1995, James 1988, Leather & James 1991 among others Suprasegmental learning Effect on foreign accent (Anderson-Hsieh et al. 1992, Munro & Derwing 1998, Trofimovich and Baker, 2006) Stress placement (Altmann 2006, Archibald 1997, 1998) Acoustic realization and perception of cues (Beckman 1986, McGory 1997, Mennen 2004, Ueyama 2001) 2

3 Prosodic features of target languages L1: Taiwan Mandarin Tone language Phonemic role of F0 Syllable-timed rhythm L2: American English Stress language F0, intensity, duration, and spectral composition Stress-timed timed rhythm 3

4 The present study Research questions How do learners utilize F0 and duration differently in production of English lexical stress? How do learners weigh these two cues in perception? Is there any correlation between production and perception? 4

5 Acoustic study Stimuli 14 word pairs: object ject-object (noun-verb) Participants 9 beginning and 9 advanced L2 learners 10 native English speakers Task Read target word in a carrier sentence, repeat the target word in isolation after each sentence. only the word produced in isolation was analyzed. Measurements Max and mean F0, duration, intensity, and F2 5

6 Examples object object Native English speakers Beginning learners Advanced learners 6

7 Results first-to to-second vowel ratios nouns 1.0 All speaker groups utilize all correlates in nouns Native speakers use max F0 and intensity to a greater extent than others 7

8 Results first-to to-second vowel ratios (verbs) 1.0 Learners utilize all correlates in verbs Native speakers rely mainly on duration 8

9 Results stressed-to-unstressed vowel ratio, noun: v1/v2, verb: v2/v1 Mean F0 Intensity noun verb Max F0 noun verb Duration noun verb noun verb 9

10 Results Max F0 Duration 1.0 noun verb noun verb Striking asymmetry in max F0 and duration realization for nouns and verbs for native speakers 10

11 Acoustic study- summary Native speakers marked asymmetry of realization in nouns and verbs reduce unstressed vowels in all conditions Beginning learners use consistent magnitudes of max F0 and duration for nouns and verbs do not always reduce unstressed vowels Advanced learners pattern between beginners and native speakers 11

12 Perception- methodology Stimulus construction Spectral composition (dada and dəda) Max F0 five first-to to-second vowel ratios Duration five first-to to-second vowel ratios 12

13 Stimulus construction- spectral composition naturally produced DAdu da DU 197 ms da0 də0 144 ms duration də1 197 ms da1 pitch tier intensity tier də2 də3 13

14 Stimulus construction Max F0 Duration 14

15 Perception- Methodology Participants 25 beginning, 25 advanced learners 25 native listeners Procedure- stress localization task DAda dada 15

16 Statistical analysis Overall analysis (four-way ANOVA) Between-subjects factor- proficiency (3) Within-subjects factors spectral composition (2) duration (5) max F0 (5) Dependent variable: localization responses DAda first syllable stressed = 1 dada second syllable stressed = 2 Spectral composition has a similar effect on all proficiencies dədada tokens receive significantly more verb responses 16

17 Results- Max F0 Proficiency (*) dada Advanced learners strong effect Native speakers gradient effect DAda Beginning learners no effect 17

18 Results- Duration Proficiency (*) Beginning learners strong effect Native speakers gradient effect Advanced learners gradient effect 18

19 Perception - Discussion Native speakers sensitive to max F0 and duration Beginning learners sensitive to small duration differences insensitive to small max F0 differences Advanced learners sensitive to max F0 and duration, with a stronger effect from max F0 cue 19

20 Cue weighting in perception noun verb noun noun Duration outweighs max F0 cue when in conflict 20

21 Max F0 in native production and perception n.s. noun verb Production use Max F0 in nouns but not in verbs Perception Same degree of max F0 difference between stressed and unstressed syllables does not trigger same degree of responses in verb contexts (chance level) as it does in noun contexts 21

22 Duration in native production and perception noun verb Production duration used to a greater extent in verbs Perception verb responses require greater duration differences 22

23 General discussion Native production and perception If a cue is not used in production in a given context, it does not affect perception in that context If a cue is used in production in a given context, perceptual sensitivity correlates with its magnitude used in production 23

24 General discussion The F0 and rhythmic features in Mandarin affect the production and perception of English lexical stress Phonemic F0 adoption of similar F0 ratios between stressed and unstressed vowels in production (in nouns and verbs) low sensitivity to small F0 differences in perception Syllable-based based rhythm causes difficulties in shortening unstressed syllable but triggers high sensitivity in perception 24

25 Conclusion Prosodic features of Taiwan Mandarin affect the acquisition of English lexical stress in both acoustic realization and perception When comparing stress realization between non-native native and native speakers, care should be taken to distinguish stress location Correlations between native production and perception warrant further investigation 25

26 Acknowledgements Experiment participants Praat scripts by Mietta Lennes, Yi Xu,, and Holger Mitterer Discussion with David Montero, Travis Wade and University of Kansas Phonetics and Psycholinguistics Laboratory members 26

27 Results - F2 syllable 1: stressed in nouns,, unstressed in verbs Vowel reduction lowering in front vowels, rising in back vowels Vowel reduction/centralization only in native production 27

28 Results- spectral composition syllable 2 Vowel reduction/centralization in all groups 28

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30 Advanced learners Max F0 outweighs duration when in conflict 30

31 Beginning learners Only sensitive to duration in all cue combinations 31

32 Advanced learners Max F0 outweighs duration when in conflict 32

33 Acoustic study 2 stimuli monkey key-key (4 pairs) participants 18 NNS (9 beg. & 9 adv.) and 10 NS measurements F0 contours 33

34 Results Learners F0 contours have greater F0 drops and the rise/plateau at the onset resembles the profile of the Mandarin high falling tone 34

35 Research questions How do learners utilize F0 and duration differently from native speakers in production of English lexical stress? Learners use consistent magnitude of F0 and duration across different stress locations Native speakers utilize max, mean F0, intensity, and duration in noun readings but rely mainly on duration for verb readings How do learners weigh these two cues in perception? Beginning learners focus on duration Advanced learners focus on max F0 Native speakers focus on both Is there any correlation between production and perception? Not found in learners Native speakers 35

36 Conclusion and future research F0 Contrastive to contrastive Contrastive to non-contrastive Non-contrastive to contrastive Duration Contrastive to contrastive Contrastive to non-contrastive Non-contrastive to contrastive 36

37 Previous research on American English Fry (1955) production stimuli: object, subject, digest, contract, permit vowel duration, intensity (F0 not measured) perception stimuli: intensity (5 levels), duration (5 levels) +10 db +5 db equal -5 db 5-10 db 37

38 Methodology Participants 25 native English speakers Mandarin L2 learners of English 25 beginning 25 advanced Procedure DAda dada 250 ms ISI 38

39 Results 100% 90% duration intensity Percentage of "noun" judgement 80% 70% 60% 50% 40% 30% 20% 10% 0% increasing ratio v1/v2 29% 70 % (adopted from Fry 1955) 39

40 Methods- procedure It is a record of your grades. read the sentence, repeat highlighted word underlined syllable is stressed 40

41 Acoustic measurements object object vowel 1 vowel 2 vowe 1 vowel Time (s) Time (s) F2 F2 F2 F2 41

42 Production- Lieberman (1960) American English 6 female and 10 male speakers Noun-Verb pair 2 listeners listen to the production twice select the stressed syllable for further processing Results stressed syllable 90% (of all cases) higher in F0 87% higher in amplitude 66% longer in duration Conclusion higher F0 and amplitude most relevant correlates 42

43 Previous research on stress in L2 French to English- Per (Fry1972) basic not as sensitive to duration as NS advanced patterns like NS Japanese to English- Per ( NNS more sensitive to F0 than NS Per (Beckman 1986) Japanese to English- Pro (Ueyama 2000) NNS use higher F0 ratio than NS Basic do not use duration; advanced pattern in between Chen et. al (2002) Mandarin to English NNS use F0, duration, and intensity as NS 43

44 Production of sentential stress Mandarin to English Ss 40 (Beijing) Mandarin speakers and 40 English speakers Stimuli I bought a cat there. I BOUGHT a cat there I I bought a CAT there. I I bought a cat THERE. measurements F 0, duration, intensity (Chen et. al. 2001) F 0 =F 0[stressed] (average F 0 [unstressed] 0 [unstressed] ) 44

45 Chen et. al. (2001)- Results --- Mandarin speaker --- English speaker F0 Duration stressed unstressed stressed unstressed Intensity stressed unstressed 45

46 Methodology- Procedure DAda dada 250 ms ISI click circle to center mouse and activate stimulus Identify the stressed syllable by clicking text max F0 ratios (5) duration ratios (5) vowel type (2) 3 repetitions 46

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49 Results- spectral composition Reduction observed only in native speakers productions degree of reduction greater in back vowels than that of front vowels. 49

50 Results- spectral composition Reduction observed in all speakers productions degree of reduction greater in back vowels than that of front vowels. 50

51 Native English speakers Native speakers have more verb responses as max F0 and duration ratio decreases (cue verbs) Effects are gradient 51

52 Beginning learners 52

53 Advanced learners 53

54 Discussion- duration asymmetry Greater duration magnitude in verbs- especially by native speakers Final lengthening enhance duration cue in verbs 54

55 Discussion- F0 and intensity asymmetry Down-stepping enhances F0 and intensity in nouns 55

56 Background Speech Learning Model Flege and colleagues (1987, 1988, 1992, 1995) Native Language Magnet Kuhl and colleagues (1989, 1991, 1992, 1994, 1998) Perceptual Assimilation Model Best