Differences in coda voicing trigger changes in gestural timing: A test case from the American English diphthong /aɪ/

Area of Science:

• Phonetics and Phonology
• Speech Production and Perception
• Articulatory Linguistics

Background:

• Vowel duration and spectral characteristics differ before voiceless versus voiced consonants.
• Existing theories propose various explanations for these acoustic differences.
• This study explores a unified source: the temporal reorganization of articulatory gestures.

Purpose of the Study:

• To test the hypothesis that acoustic differences in vowels before codas stem from temporal reorganization of articulatory gestures.
• To investigate the role of temporal gestural distance in producing and perceiving voicing contrasts.
• To examine the American English diphthong /aɪ/ as a case study.

Main Methods:

• Experiment 1: Measured the ratio of nucleus-to-offglide duration for the diphthong /aɪ/ in production before voiceless and voiced codas.
• Experiment 1: Analyzed the effect of speech rate and phrasal position on this ratio.
• Experiment 2: Assessed listeners' perception of diphthongs with contextually incongruent nucleus-to-offglide ratios before voiceless codas.

Main Results:

• Production: The nucleus-to-offglide duration ratio was smaller before voiceless codas than before voiced codas, consistent across speakers and conditions.
• Perception: Listeners showed delayed word identification when diphthongs had contextually incongruent ratios, even with intact voicing cues.
• These findings indicate sensitivity to the temporal gestural origins of voicing differences.

Conclusions:

• The voicing contrast in codas influences the temporal organization of preceding articulatory gestures.
• Gestures are temporally closer before voiceless codas and further apart before voiced codas.
• Listeners are sensitive to these timing variations, supporting a gestural account of phonetic variation.