Articulatory modeling of the S-shaped F2 trajectories observed in Öhman's spectrographic analysis of VCV syllables
Frédéric Berthommier
TL;DR
The work addresses the lack of articulatory models for Öhman's S-shaped F2 transitions in VCV coarticulation. It adopts the Maeda articulatory model with Tau-based trajectory planning to synthesize the same 75 VCV sequences and to separate vowel- and consonant-driven planning while preserving observed F2 behavior. It provides a reinterpretation of locus equations within an articulatory framework and demonstrates that the S-shaped F2 arises from coordinated interactions across all articulators, not a simple vowel-driven sigmoid. The approach yields reproducible, interpretable insights into syllable planning and coarticulation, with open-source code enabling further integration with data-driven representations like Sylber.
Abstract
The synthesis of Ohman's VCV sequences with intervocalic plosive consonants was first achieved 30 years ago using the DRM model. However, this approach remains primarily acoustic and lacks articulatory constraints. In this study, the same 75 VCVs are analyzed, but generated with the Maeda model, using trajectory planning that differentiates vowel-to-vowel transitions from consonantal influences. Synthetic data exhibit similar characteristics to Ohman's sequences, including the presence of S-shaped F2 trajectories. Furthermore, locus equations (LEs) for F2 and F3 are computed from synthetic CV data to investigate their underlying determinism, leading to a reassessment of conventional interpretations. The findings indicate that, although articulatory planning is structured separately for vowel and consonant groups, S-shaped F2 trajectories emerge from a composite mechanism governed by the coordinated synergy of all articulators.