Single-channel vibrotactile supplements to visual perception of intonation and stress

Two experiments were conducted to explore the effectiveness of a single vibrotactile stimulator to convey intonation (question versus statement) and contrastive stress (on one of the first three words of four 4- or 5-word sentences). In experiment I, artificially deafened normal-hearing subjects judged stress and intonation in counterbalanced visual-alone and visual-tactile conditions. Six voice fundamental frequency-to-tactile transformations were tested. Two sentence types were voiced throughout, and two contained unvoiced consonants. Benefits to speechreading were significant, but small. No differences among transformations were observed. In experiment II, only the tactile stimuli were presented. Significant differences emerged among the transformations, with larger differences for intonation than for stress judgments. Surprisingly, tactile-alone intonation identification was more accurate than visual-tactile for several transformations.