Nasal coarticulation in Lombard speech

Abstract

Speaking in noisy environments entails a multitude of adaptations to speech production. Such modifications are expected to reduce gestural overlap between neighbouring sounds in order to enhance their distinctiveness, yet evidence for reduced coarticulation has been ambiguous. Nasal coarticulation in particular presents an unusual case, as it has been suggested to increase instead in certain clear speech conditions. The current study presents an experiment aimed at investigating how use of nasal coarticulation varies in quiet and noisy speech conditions. Speakers of Southern British English were recorded using a nasometer in an interactive reading task and produced monosyllabic target words with vowels bound by combinations of stop and nasal consonants. Use of nasal coarticulation was compared by means of a normalised measure that takes into account the speaker- and vowel-specific range of nasalisation available in each condition. In two noisy conditions where the interlocutor was either visible or not, vowel nasality in coarticulatory contexts was found to decrease in a way that closely tracked the compressed range between oral and nasal baselines. Speakers thus maintained their use of nasal coarticulation in Lombard speech, especially in the anticipatory direction. These findings suggest that the spreading of the velum lowering gesture from nasal consonants to neighbouring vowels is not targeted for adaptation in Lombard speech. They further reaffirm that enhancing acoustic distinctiveness and maintaining coarticulation are joint, compatible goals in the production of hyperarticulated speech.