Audiovisual enhancement in clear speech production of English laterals

Abstract

<p>The role of auditory perceptibility in the maintenance and enhancement of phonological contrast<br>is well established. In clear speech styles, speakers are observed to increase the acoustic distance<br>between contrastive phones to improve auditory perceptibility. Non-auditory perceptual cues<br>(notably vision) also influence speech perception and have long been known to improve<br>perceptibility under noisy conditions. As such, clear speech may also involve enhancement of<br>visible articulations, e.g., lip rounding. The finding that blind speakers show less rounding than<br>sighted speakers in clear speech suggests that such modifications are at least partly mediated<br>by visual factors. Yet while increasing the degree of lip protrusion may improve visual<br>perceptibility, doing so simultaneously increases acoustic distance by lowering F2. In many cases<br>it is therefore difficult to determine the extent to which speakers are optimizing their speech for<br>auditory-acoustic and/or visual-articulatory cues.</p><p><br>To address this question, we investigate the production of laterals and other coronal consonants<br>in normal and listener-oriented clear speech. In English, visibly articulated variants of /l/ have been<br>noted to occur in lip syncing and can also be observed in other clear or emphatic speech styles.<br>Such variants have not been systematically investigated, however, so their frequency, phonetic<br>properties, and phonological distribution, as well as their communicative function, remain<br>unknown. The goal of this study is to examine how speakers use visible articulatory gestures in<br>producing English laterals during clear speech, to test the hypothesis that some articulatory gestures<br>serve a visuoperceptual rather than auditory enhancement function.</p>