The transmission of phoneme-level information by multichannel tactile speech perception aids

Current research on the effectiveness of tactile aids for speech perception by hearing-impaired persons suggests that substantial training, lasting over months or years, is necessary for users to achieve maximal benefits from a tactile device. A number of studies have demonstrated the usefulness of training programs that include an analytic component, such as phoneme training, together with more synthetic tasks such as sentence identification and speech tracking. However, particularly in programs for children, it is desirable to structure training experiences so that easy distinctions are trained first, and more difficult distinctions are approached only later in training. In the present study, a systematic evaluation of phoneme-level information provided by the Tactaid VII, a multichannel tactile aid, was performed. Adult subjects were tested in minimal pairs and closed set phoneme discrimination and identification tasks under tactile aid alone, speechreading alone, and speechreading plus tactile aid conditions, to provide an inventory of stimulus identifiability and permit ranking of discriminations as easy or more difficult. Because these rankings might differ as a function of coarticulation effects, three different vowel contexts were tested for consonant stimuli. Results indicated that there were indeed considerable differences across vowel contexts, and that the /ae/ vowel context yielded the most identifiable stimuli. These data could be used by teachers and therapists to construct viable stimulus sets for training programs for tactile aid users.