Perceived prominence and nuclear accent shape Rachael-Anne Knight LAGB 5 th 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’ Frequency 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 AnnaManny

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, peak210 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 Hz for the peak series  This difference is significant (p=0.000)

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

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 activity  Plateaux 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