Auditory feedback perturbation of vowel production: A comparative study of congenitally blind speakers and sighted speakers

Abstract

Studies with congenitally blind speakers show that visual deprivation yields increased auditory discrimination abilities as well as reduced amplitude of labial movements involved in vowel production, compared with sighted speakers. To further investigate the importance of auditory and visual feedback in speech, a study of auditory perturbation of rounded vowels was conducted in congenitally blind and sighted French speakers. Acoustic and articulatory (electromagnetic articulography) recordings from ten congenitally blind speakers and ten sighted speakers were obtained during the production of the French rounded vowel /ø/. All participants were first asked to produce the vowel repeatedly in a normal condition, i.e., with regular auditory feedback. In the perturbed condition, participants received, in real-time through headsets, an altered version of their speech, in which F2 was gradually increased up to 500 Hz. To compensate for this perturbation, speakers had to enhance lip protrusion and/or tongue retraction. These adaptive maneuvers should have been concurrent with auditory perception abilities. Preliminary results show that congenitally blind speakers gave greater weight to auditory perception than their sighted peers, while compensating differently for the perturbations. These findings support the hypothesis that vision plays a significant role in the implementation of phonological targets.

Maintaining Distinctiveness at Increased Speaking Rates: A Comparison between Congenitally Blind and Sighted Speakers

“…In contrast, since perceptual saliency does not involve visual distinctiveness for them, blind speakers would have safeguarded auditory goals more than their sighted peers, thus producing vowels within the appropriate auditory regions of the language. These results can be related to those obtained in a different study in which compensatory abilities to auditory perturbation were investigated in blind and sighted speakers [4,25]. In the latter study, participants were asked to produce the vowel /ø/ while hearing a vowel in which F2 was altered towards /e/.…”

“…In blind individuals, visible lip gestures are weighted less heavily in the phonemic target than they are in sighted speakers, and thus they are recruited less in contexts where (multimodal) intelligibility is enhanced. However, in cases where the phonemic goal is jeopardized, such as in auditory perturbation experiments, blind speakers use larger displacements of the lips (visible) and tongue (invisible) articulators to compensate for the perturbation and preserve the auditory phonemic goal [4]. To better understand the impact of visual deprivation on the strategies used to preserve speech goals, the current study focuses on increased speech rate, which is known to affect vowel duration and contrasts.…”

“…Since congenitally blind and sighted speakers of French showed differences in the way they altered acoustic values in contexts where the phonemic goal was jeopardized [4], the current study was designed to investigate the effect of variations in the speaking rate on the acoustic components of vowels in congenitally blind and sighted French-Canadian adults. …”