Impact of prosodic structure and information density on dynamic formant trajectories in German

Abstract

This study investigated the influence of prosodic structure and information density (ID), defined as contextual predictability, on vowel-inherent spectral change (VISC). We extracted formant measurements from the onset and offset of the vowels of a large German corpus of newspaper read speech. Vector length (VL), the Euclidean distance between F1 and F2 trajectory, and F1 and F2 slope, formant deltas of onset and offset relative to vowel duration, were calculated as measures of formant change. ID factors were word frequency and phoneme-based surprisal measures, while the prosodic factors contained global and local articulation rate, primary lexical stress, and prosodic boundary. We expected that vowels increased in spectral change when they were difficult to predict from the context, or stood in low-frequency words while controlling for known effects of prosodic structure. The ID effects were assumed to be modulated by prosodic factors to a certain extent. We confirmed our hypotheses for VL, and found expected independent effects of prosody and ID on F1 slope and F2 slope.