Tactile-auditory speech perception by unimodally and bimodally trained normal-hearing subjects

The following study compared the effectiveness of unimodal and bimodal training strategies at improving the perception of speech information under a variety of conditions. Normal-hearing subjects were trained in the perception of vowel and consonant stimuli. Speech information was provided either via a multiple channel electrotactile speech processing aid (the Tickle Talker), and/or by a 200-Hz low-pass filtered auditory signal. Two subjects were trained only in the combined tactile-plus-auditory (TA) condition; the remaining two were trained in both the tactile-alone (T) and auditory-alone (A) conditions; however, only one condition was used at any single time. All subjects were evaluated in the TA, T, and A conditions, both at the beginning of the study, prior to training, and at the completion of training, on closed-set vowel and consonant confusion tests, and on an open-set word test. Results indicated that whilst statistically significant improvements occurred from one evaluation period to the next, in both groups of subjects, the improvements per condition were not dependent on the type of training received. The results provide a preliminary indication that the provision of unimodal training does not impair the perception of speech information under bimodal perception conditions.