Perceived prominence and nuclear accent shape

Rachael-Anne KnightLAGB

5th September 2003

Outline

The perception of pitch Plateaux and contour shape The effect of shape on pitch perception Pitch and prominence The effect of shape on prominence perception Sound symbolism Plateau production Conclusions

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 Explained as the listener

‘normalising for declination’

Freq

uenc

y

Time

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)

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

How does the plateau affect the perception of pitch?

3 possible hypotheses No effect A longer plateau makes a syllable sound higher

in pitch A longer plateau makes a syllable sound lower

in pitch

Pilot Experiment – Stimuli

Test sentence “…came with Manny” taken from “Anna came

with Manny”

Resynthesised nuclear accent (12 versions) Frequency of contour

o 160, 180, 200, 210 Hz Shape of contour

o Peak, 50ms or 100 ms plateau

Examples of different contours

Anna Manny

Pilot Experiment – Procedure

7 Subjects heard pairs of sentences ‘Manny’ differed only in shape never in pitch

Asked “In which version is ‘Manny’ higher in pitch?”

Responded by pressing 1 or 2 on a keyboard

160 Hz plateau, peak 210 Hz peak, plateau

Pilot Experiment – Results

73% of responses were for “plateau sounds higher” (p<0.05) This result held at each of the 4 frequencies

Both lengths of plateau sounded higher than the peak

There was no significant difference between the two lengths of plateau Suggesting a categorical rather than gradient effect

So, syllables sound higher in pitch with a plateau in the contour

Pitch and Prominence

There is a close association between pitch height and prominence

“Linguistically, the size of …F0 excursions … correlate[s] 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

Prominence Ask about prominence in addition to height Relations within an utterance Test more subjects

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

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

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

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

Universal biological codes link the form of intonation to meaning

The frequency code Deference, politeness > interrogativity

The production code Higher accents at beginnings > initiality

The effort code More effort, higher pitch > emphasis

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

Delayed peaks as substitute variable for pitch height

Production code (Wichmann and House 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 sounds 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

The plateau as a substitute variable

As the plateau’s effect is to increase the perceived height and prominence

It may be a substitute for increased peak height taking advantage of the effort code

Allowing speaker to increase the prominence of the nucleus

The Plateau in Production

Why should a speaker produce a plateau rather than simply a higher peak?

Answer may lie in the structure and function of the larynx

The Larynx

Contraction of cricothyroid muscle:Controls the movement of the cricothyroid joint

Rotates the thyroid cartilage downward and forward

Lengthens and stretches the vocal folds

Cricothyroid Activation

Higher peaks are associated with greater activityPlateaux are associated with sustained activity(Collier 1975)

The Plateau in Production (2)

Plateaux mainly occur in nuclear position in broad focus declaratives The nucleus is at the end of the utterance Subglottal pressure is low due to declination

Speaker has to work harder to produce higher peaks

More energy efficient to add prominence by producing a plateau

Conclusions

The plateau increases the perception of pitch height and prominence

The plateau is a substitute variable for peak height under the umbrella of the effort code

It allows the speaker to create the perceptual effect of added height and prominence

Without having to step outside the physiologically determined slope of declination