nuclear accent shape and the perception of prominence

Nuclear Accent Shape and the Perception ofProminence

Rachael-Anne Knightrachaelanne@cantab.net

Prosody and Pragmatics

15th November 2003

Outline

The perception of pitchPlateaux and contour shapePitch and prominenceThe effect of shape on prominence

perceptionSound symbolismConclusions

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

The Perception of Pitch – Syllable Position

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

Freq

uenc

y

Time

Explained as the listener ‘normalising for declination’

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

Peak 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

Peak

4% range

Plateau

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

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)

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

Pilot Experiment*

Subjects heard pairs of sentences where nuclear accent differs only in shape (peak vs. plateau) not frequency

Knight (2003)

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)

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)

Prominence Experiment

Hypothesis Subjects will accept an accent as the most

prominent at a lower frequency when there is a plateau (rather than a peak) in the contour

EqualPitch

EqualPitch

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

Examples of different contours

Anna Manny

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. Plateau220 Hz. Peak

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

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)

0102030405060708090

100

160 170 180 190 200 210 220

Frequency (Hz)

% o

f Man

ny r

espo

nses

Peak Plateau

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)

0102030405060708090

100

160 170 180 190 200 210 220

Frequency (Hz)

% o

f Man

ny r

espo

nses

Peak Plateau

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

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

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)

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

Plateaux as substitute variables

Plateaux occur in the same environments as peak delay: In paragraph initial position (Wichmann et al. 1999)

o Production code In questions in Neapolitan Italian (D’Imperio 2002)

o Frequency code

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

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

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