Nuclear Accent Shape and the Perception of Prominence

1. Nuclear Accent Shape and the Perception ofProminence Rachael-Anne Knight rachaelanne@cantab.net Prosody and Pragmatics 15th November 2003

2. Outline • The perception of pitch • Plateaux and contour shape • Pitch and prominence • The effect of shape on prominence perception • Sound symbolism • Conclusions

3. The Perception of Pitch -F0 • The perception of the pitch of a complex sound is related to the fundamental frequency • Sounds that have a higher fundamental frequency sound higher in pitch

4. In an utterance the position of a syllable also affects the perception of pitch If two syllables have identical F0, the one later in the utterance will sound higher in pitch The Perception of Pitch – Syllable Position Frequency Time • Explained as the listener ‘normalising for declination’

5. Plateau Peak Contour Shape • Real contours are not stylised peaks and troughs • The majority of falling nuclear accents are realised as more of a flat stretch of contour

6. Peak 4% range Plateau Definition of the Plateau • Plateaux are defined as being 4% down from any absolute peak in F0 • 4% is the range of perceptual equality

7. Segmental and Prosodic Effects on the Production of the Plateau • Plateaux: • Begin earlier in syllables with sonorant onsets • Take up more of syllables that have sonorant onsets and codas • Are aligned later in the syllable in polysyllabic than monosyllabic feet

8. The End of the Plateau • Some speakers align the end of the plateau earlier in the syllable before a word boundary • The end of the plateau is stably aligned within the syllable regardless of pitch span • More errors made with incorrect EP alignment in a true/false judgment task • The end of the plateau seems to be the real target (rather than the peak) (Knight 2002)

9. The Function of the Plateau • What is the plateau for? • Why do speakers produce plateaux in nuclear position? • No physiological reason that requires them to produce a plateaux • Perhaps the plateau affects the perception of the pitch (and  the prominence) of the nuclear syllable

10. Pilot Experiment* • Subjects heard pairs of sentences where nuclear accent differs only in shape (peak vs. plateau) not frequency Knight (2003)

11. Pilot Experiment* • Subjects heard pairs of sentences where nuclear accent differs only in shape (peak vs. plateau) not frequency • Asked in which version accent sounds higher • 73% of responses favoured plateau stimuli Knight (2003)

12. Pitch and Prominence • “Linguistically, the size of … F0 excursions … correlate with the prominence of the accent” • Gussenhoven and Rietveld (1985:299) • BUT… • “Perceived prominence is related in a complex way to the range of F0 values employed” • Terken (1990:1768)

13. Equal Pitch Equal Pitch Prominence Experiment • Hypothesis • Subjects will accept an accent as the most prominent at a lowerfrequency when there is a plateau (rather than a peak) in the contour

14. Prominence Experiment – Stimuli • Test sentence “Anna came with Manny” • Resynthesised nuclear accent (14 versions) • Frequency: 160, 170, 180, 190, 200, 210, 220 Hz • Shape: peak or 100ms plateau • 2 tokens of each version quasi-randomised together

15. Examples of different contours Anna Manny

16. Prominence Experiment – Procedure • 24 subjects listened to each version over headphones • 12 asked “Is ‘Anna’ or ‘Manny’ higher in pitch?” • 12 asked “Is ‘Anna’ or ‘Manny’ more prominent?” • Responded by pressing buttons marked A and M on a keyboard 220 Hz. Plateau 220 Hz. Peak

17. Prominence Experiment-Statistics • Probit analysis • To identify the cross-over point for each series for each subject (where ‘Anna’ and ‘Manny’ are of equal prominence / pitch) • Paired Sample T-Test • To see if the cross-over point occurs at a lower frequency in the plateau series

18. Prominence Experiment – Height Results • The cross-over point occurs at 190 Hz for the plateau series and 200.6 Hz for the peak series • This difference is significant (p=0.000)

19. Prominence Experiment – Prominence Results • The cross-over point occurs at 196.1 Hz for the plateau series and 209.0 Hz for the peak series • This difference is significant (p=0.000)

20. Experiment Conclusions • The shape of the pitch contour does affect judgements of height and prominence • Perceived pitch is a close correlate of prominence • The function of the plateau may be to add to the prominence of the nuclear syllable

21. Sound Symbolism • The frequency code • smaller larynx = higher pitch • Deference, politeness > interrogativity • The production code • higher subglottal pressure = higher pitch • Higher accents at beginnings > initiality • The effort code • more effort = higher pitch • Larger excursions > emphasis / prominence

22. Substitute variables* • The physiological mechanism behind each code do not have to be created • Only the perceptual effect has to be created • For example, late peaks can be substituted for high peaks as they create the same perceptual effect Gussenhoven(2002)

23. Delayed peaks as substitute variable for pitch height • Production code (Wichmann et al. 1999) • Peaks are later in more initial accents • Effort code (Ladd and Morton 1997) • Peaks are later in more emphatic accents • Stimuli with later accents sound more emphatic • Frequency code (Gussenhoven and Chen 2000) • Peaks are later in questions in many languages • Stimuli with accents timed later sound more like questions

24. Plateaux as substitute variables • Plateaux occur in the same environments as peak delay: • In paragraph initial position (Wichmann et al. 1999) • Production code • In questions in Neapolitan Italian (D’Imperio 2002) • Frequency code

25. The nuclear plateau as a substitute variable • As the nuclear plateau’s effect is to increase perceived height and prominence… • …it may be a substitute variable for increased peak height • taking advantage of the effort code • Allowing speaker to increase the prominence of the nucleus • counteracting the effect of declination

26. Conclusions • The plateau is a substitute variable for peak height • Nuclear plateaux increase the perception of pitch height and prominence of the nucleus • Plateau allows the speaker to create this effect without having to step outside the physiologically determined slope of declination

27. Questions?

28. References • D’Imperio, M (2002) “Language specific and universal constraints on tonal alignment: The nature of targets and “anchors”, in Bel, B, and I. Marlien (eds.) Proceedings of the Speech Prosody 2002 conference, Aix-en-Provence, 101-106 • Gussenhoven, C. (2002) “Intonation and interpretation: Phonetics and phonology in Bel, B, and I. Marlien (eds.) Proceedings of the Speech Prosody 2002 conference, Aix-en-Provence, 47-57 • Gussenhoven, C. and T. Rietveld, (1995) “ On the relation between pitch excursion size and prominence”, Journal of Phonetics, 13, 299-308 • Gussenhoven, C. and A. Chen, (2000) “Universal and language specific effects in the perception of question intonation” Proc ICSLP, 6, 91-94 • Knight (2002) “The influence of pitch span on intonational plateaux” in B. Bel and I. Marlien (eds.) Proceedings of the Speech Prosody 2002 conference, Aix-en-Provence, 439-442 • Knight (2003) “Nuclear accent shape and the perception of syllable pitch”, Paper presented at LAGB, 16 April 2003 • Ladd, D. and R. Morton, (1997) “The perception of intonational emphasis: continuous or categorical?” Journal of Phonetics, 25, 313-342 • Terken, J. (1999) “Fundamental frequency and perceived prominence of accented syllables” JASA, 89, 4, 1768-1776 • Wichmann, A, J. House and T. Rietveld (1999) “Discourse constraints on peak timing in English: Experimental evidence” Proc. XIVth ICPhS 1765-1768