A minimal dynamical model of Intonation: Tone contrast, alignment, and scaling of American English pitch accents as emergent properties

Abstract

The pitch accent system of Mainstream American English (MAE) is one of the most well-studied phenomena within the Autosegmental-Metrical (AM) approach to intonation. In this work we present an explicit model grounded in dynamical theory that predicts both qualitative phonological and quantitative phonetic generalizations about the MAE system. While the traditional AM account separates a phonological model of the structure of the accents from the F0 algorithm that interprets the phonological specification, we propose a unified dynamical model that encompasses both. The proposed model is introduced incrementally, one dynamical term at a time, to arrive at the minimal model needed to account for observed empirical generalizations, avoiding unnecessary complexity. The quantitative and qualitative properties of the MAE system that inform the dynamical model are based on an analysis of a large database of productions of the four most well-studied pitch accents of American English: three rising accents (H*, L+H*, L*+H) and a low-falling accent (L*). The dynamic model highlights the importance of velocity-based measures of F0, not typically invoked in intonational research, as key to understanding F0 differences among pitch accent categories. Although the focus of this work is on the MAE pitch accent system, suggestions are made for how the unified phonetic-phonological dynamical framework presented can be further developed to account for other pitch-based phenomena in a variety of languages.