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Nuclear Accent Shape and the Perception of Pitch and Prominence

Nuclear Accent Shape and the Perception of Pitch and Prominence. Rachael-Anne Knight rachaelanne@cantab.net BAAP 25 March 2004. Outline. The perception of pitch Nuclear accent shape – the plateau The experiment The plateau as a substitute variable for pitch height.

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Nuclear Accent Shape and the Perception of Pitch and Prominence

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  1. Nuclear Accent Shape and the Perception ofPitch and Prominence Rachael-Anne Knight rachaelanne@cantab.net BAAP 25 March 2004

  2. Outline • The perception of pitch • Nuclear accent shape – the plateau • The experiment • The plateau as a substitute variable for pitch height

  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. What do we already know about the plateau? • Plateaux take up more of syllables that have sonorant onsets and codas • Plateaux are aligned later in the syllable in polysyllabic than monosyllabic feet • Some speakers align the end of the plateau earlier in the syllable before a word boundary • The end of the plateau is stably aligned in the syllable regardless of pitch span • The end of the plateau may be used as a cue in spoken word recognition

  8. 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

  9. Pilot experiment • Subjects listened to pairs or sentences which differed only in whether the shape of the nuclear accent was a peak or plateau • Results showed that plateau-shaped accents sounded higher in pitch • But is pitch equivalent to prominence?

  10. Equal Pitch / Prominence Equal Pitch / Prominence 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

  11. 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

  12. Examples of different contours Anna Manny

  13. 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

  14. 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

  15. 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)

  16. 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)

  17. 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 indeed be to add to the prominence of the nuclear syllable

  18. The plateau as a substitute variable for pitch height • As the plateau’s effect is to increase perceived height and prominence… • …it may offer an alternative to increasing pitch height… • …counteracting the effect of declination in an ‘energy-efficient’ manner

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

  20. Questions?

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