Speech feature encoding through an electrotactile speech processor Robert

Efficiency of speech feature encoding by the University of Melbourne multichannel electrotactile speech processor was assessed through performance of eight subjects on a closed-set tactual test battery. The battery consisted of 12 subtests, each assessing discrimination of a particular speech feature in an ABX paradigm. All subjects scored significantly above chance on suprasegmental features such as syllable number, stress, and vowel length. Discrimination of vowel formant contrasts was significantly above chance for seven subjects. Discrimination of consonant manner varied across specific subtest contrasts, with better encoding of the high-frequency fricatives and affricates. Discrimination of initial voicing contrasts suggested that tactual encoding of this feature could be improved. Comparison of these results with test battery scores from five different subjects with five commercially available tactile devices showed superior encoding of vowel formant and manner contrasts by the Tickle Talker. Subsequent consonant confusion studies with two hearing-impaired adults, one using tactual input in combination with lipreading and one in combination with aided residual hearing and lipreading, confirmed that added tactual information reduced the proportion of manner confusions and to a lesser extent voicing confusions.