Calibrating rhythm: First language and second language studies

Abstract

This paper presents a comparative evaluation of metrics for the quantification of speech rhythm, comparing pairwise variability indices (nPVI-V and rPVI-C) and interval measures (ΔV, ΔC, %V), together with rate-normalised interval measures (VarcoV and VarcoC). First, we examined how well these metrics discriminated “stress-timed” English and Dutch and “syllable-timed” Spanish and French. Metrics of interval standard deviation such as ΔV and ΔC were strongly influenced by speech rate, but rate-normalised metrics of vocalic interval variation, VarcoV and nPVI-V, were shown to discriminate between hypothesised “rhythm classes”, as did %V, an index of the relative duration of vocalic and consonantal intervals. Second, we applied these metrics to quantifying the influence of first language on second language rhythm, with the expectation that speakers switching “rhythm classes” should show rhythm scores different from both their native and target languages. VarcoV offered the most discriminative analysis in this part of the study, with %V also suggesting insights into the process of accommodation to second language rhythm.