Magnitude and timing of acceleration peaks in stressed and unstressed syllables

Segment transitions can be accounted for by acceleration peaks, which appear at the edges of articulatory speech postures. The present study builds on previous research on timing of acceleration, and expands it by investigating magnitude of acceleration peaks at segment offset, comparing stressed and unstressed syllables. Acceleration peaks of lower lip and lower jaw are measured on ten Swedish speakers using EMA methodology. Results show strong correlation between acceleration and velocity peak magnitude, with overall more magnitude in stressed syllables, and highest acceleration peaks on lower lip. However, timing of the acceleration peaks, as measured from minimal velocity, is not affected by how fast the articulators are moving. The results reveal possible different functions of acceleration peak magnitude vs timing, also between the two articulators. The study stresses the significance of mapping acceleration peaks in speech for use in prosodic research.