Cross-linguistic variability in audiovisual enhancement of coronal consonants

Abstract

The role of auditory perceptibility in phonological contrast is uncontroversial. In clear speech, speakers increase acoustic distance between contrastive phones, thereby improving perception. Although visual cues are also known to improve perception, it is unclear whether speakers actively enhance their speech for visual perceptibility. 20 native English and 20 native Mandarin speakers participated in a two-part production experiment. Words containing /l d n s r/ (and English /θ/) were elicited, with vowels balanced for height, backness, and rounding. Speakers first recited each word while alone in a soundproof booth. Words were then spoken for a native listener (who attempted to guess the word) over Zoom with heavily degraded audio. Audio and high-speed video were recorded. English speakers showed a significant increase in visually exaggerated articulations for /l, θ/ (but not /n, d, s, r/), including interdental and linguolabial productions with external lingual protrusion. Mandarin speakers increased their use of interdental articulation for /n, l, t, s/ (but not /r/), although lingual protrusion was limited. These results demonstrate that speakers may enhance their speech for visual over auditory perceptibility but suggest that enhancement is mediated by language-specific factors including phonological contrast and the articulatory characteristics of sounds in normal speech.