Description:

Decades of work on speech variability by linguists and speech scientists has shed much light on its structure and sources, but has largely consisted of fine-grained studies of a handful of phonetic cues and languages (e.g. VOT, English), whose scope is limited by the fact that collecting and annotating speech data is time-consuming and expensive. This talk describes two studies of sound systems in large cross-linguistic corpora of read speech, which scale up relative to previous work, in terms of cross-linguistic coverage and sample size. We are able to scale up in part by using new speech analysis software enabling “large-scale studies” of sound systems, which I briefly describe.

Study 1: Sound change commonly arises from "phonetic precursors": small phonetic effects assumed to hold across languages and individuals, which evolve into full-blown contrasts over time. Relatively little is known about the robustness of most phonetic precursors: variability in their effect size across languages and speakers, which matters for establishing which precursors are robust enough to plausibly lead to change. Two widely-studied precursors, which also form a good test case for an automated analysis, are the effect of vowel height and preceding consonant voicing on F0 (VF0 and CF0). We assess the degree of cross-linguistic and interspeaker variability in VF0 and CF0 effects across 14 languages. We find that the existence of VF0 and CF0 effects are relatively robust across languages, confirming that they are possible phonetic precursors to sound changes, but their robustness across speakers is less clear, possibly helping explain why they rarely do lead to sound change. A methodological finding is that VF0 and CF0 effects can be detected in non-laboratory speech with minimal statistical controls, despite not accounting for many factors greatly affecting F0 (e.g. intonation).

Study 2: “Duration compression effects”, such as polysyllabic shortening and Menzerath’s Law, refer to the tendency for the same linguistic unit to have a shorter duration in longer words (e.g. initial syllables: stick, sticky, stickiness). Despite a long literature on individual languages, it is unclear whether DCEs are universal: they may be artefacts of language-speciifc prosodic structure, or of other speech timing effects (e.g. “final lengthening”). Using read-speech data from 19 typologically-diverse languages, we examine the universality of DCEs, and whether they can be reduced to other factors. We broadly find that DCEs look similar across languages — especially compression of average syllable length — after basic controls for other factors (e.g. speech rate). However, DCEs seem to be overridden by other factors in certain cases, such as phrase-final position.