CODING OF ACOUSTIC FEATURES FOR A SINGLE-CHANNEL TACTILE AID

Measurements have been made on the discrimination of speech contrasts on the basis of single-channel vibrotactile presentation of a variety of speech-derived signals, coded as amplitude- and frequency-modulated pulse trains. Stimulation was at the index fingertip. The signals cho sen for tactile presentation were the speech amplitude envelope, the v oice fundamental frequency FO and the zero-crossing frequency in the 1 .3-6.6 kHz band. 'Two-feature' codings, which present two of these sig nals simultaneously (one coded as stimulus frequency and one coded as stimulus amplitude), were found to be no more effective than 'single f eature' codings which present only one signal (coded as both amplitude and frequency). Scores for consonant discrimination were highest for the single-feature coding of zero-crossing frequency, although differe nces between the codings were not, in general, significant. Scores for emphatic-stress discrimination were highest for the single-feature co ding of FO, and this coding produced best results overall. A practical wrist worn device, whose design is influenced by these experimental r esults, is briefly described.