Obstruent production by hearing-impaired speakers: interarticulator timing and acoustics.

This study examines the organization of laryngeal control and interarticulator timing in the production of obstruents and obstruent clusters by three severely-profoundly deaf adults. Glottal activity was monitored by transillumination; temporal patterns of oral articulation (lips and tongue-palate) were recorded using an electrical transconductance technique. For each of the deaf speakers, an inappropriate abduction gesture was often found between words, a pattern never observed for hearing speakers. At the same time, the deaf speakers differed from each other with respect to types of errors, variability, and interarticulator coordination. For the most intelligible speaker, the timing of glottal opening with respect to oral articulation was most like that observed for normals. The second deaf speaker often failed to observe voicing contrasts with respect to glottal opening. This subject was nevertheless consistent in producing most plosives without a glottal opening, and all fricatives with an opening gesture. For the third deaf speaker, the pattern of errors was more complex and included both missing and inappropriate glottal opening gestures.