Acoustical impacts of blindness on speech production strategies linked to Lombard speech and audiovisual interaction

This paper investigates the acoustical correlates of Lombard speech and audiovisual interaction, in blind and sighted adults. Ten blind and nine sighted adults were recorded while producing repetitions of the French vowels /i/, /u/, /a/ in a “pVp” context. Sentences were produced under four conditions, varying in terms of interaction type (whether the speaker could be heard and seen—audiovisual interaction—or only heard— auditory interaction—by the interlocutor) and presence/absence of noise. Inter-vocalic and intra-vocalic formant dispersion as well as fundamental frequency (F0), intensity and vowel duration values were measured. Results of linear mixed effects models showed that blind speakers increased their inter-vocalic distances in noise, but decreased it when they were told they were seen by the interlocutor (audiovisual interaction). Blind speakers decreased F0 in the audiovisual conditions while sighted speakers increased F0 in noise. Finally, sighted speakers produced louder vowels in the noisy conditions and in the auditory interactive conditions. This pattern was only found for unrounded vowels in blind speakers. These results highlight the role of vision on speech production and show that sighted speakers likely use active strategies to enhance visual cues in audiovisual interactions, compared to auditory only interactions.