Enhancement of intonational contrasts in American English

We test a subset of intonational contrasts proposed in the Autosegmental-Metrical model for American English for evidence of contrast enhancement in phonologically and phonetically longer vs. shorter intervals. F0 trajectories were assessed from 32 speakers’ imitated productions of six tonally distinct tunes, e.g., HHH, HHL. Maximally three tune shapes emerge from clustering analyses of imitated f0 trajectories, each cluster comprising imitations of two phonetically similar but phonologically distinct tunes. We find enhancement of tune contrasts between the emergent clusters in measures of f0 differences (RMSD, end f0, center of gravity). There is no evidence of enhancement for phonetically similar tunes grouped within the same cluster, though fine-grained phonetic distinctions are detected for these “lost” tune contrasts, suggesting a reanalysis as within-category variation.