Lip protrusion and tongue position in French vowels produced by blind speakers and sighted speakers

Abstract

The influence of visual experience in speech production was investigated through a study of the French vowels /i y u a/. Articulatory and acoustic recordings of ten repetitions of the vowels in CVC syllables embedded in carrier sentences were conducted in three consonant environments (/b d g/) and two prosodic conditions (neutral and under contrastive emphasis). Six congenitally blind adults and six sighted adults were recorded. All participants were native speakers of Canadian French and had no history of speech disorder. The audio signal, lip movement, and tongue shapes were recorded using a digital camera and an ultrasound system. The minimal (for /i a/) or maximal (for /y u/) horizontal position of the upper lip was tracked and the front-back position of the tongue was measured for each vowel. Formant frequencies were extracted using LPC analyses. Results show that, despite similar acoustic differences, the rounded and unrounded vowels are less differentiated along the protrusion dimension for blind speakers compared to sighted speakers. It is suggested that this variability is related to a trade-off between lip protrusion and tongue position. Significant interaction effects between consonant environment and vowel category are discussed for each speaker group. [Work supported by SSHRC, NSERC.]