Laboratory projects in tactile aids to lipreading.

Four studies are reported on the design of tactile aids to lipreading conducted at Central Institute for the Deaf, St. Louis. A speech feature aid represented resonance, envelope, and source characteristics of speech on three vibrators at the fingertips. Artificially-deafened and congenitally deaf adults lipreading with the aid obtained an average of 40% gain over lipreading alone on syllable identification tests, but minimal gain for untrained words. In a series of three other studies, the quality of tactile sensation was developed as a cue to spectral information, presented in a temporal code based on the overall time-intensity waveform of speech. Electrical and vibratory stimulation on the hand and torso were evaluated by artificially-deafened adults using the tracking technique with connected speech. Short-term training yielded variable increments over unaided lipreading scores and lipreading with a simple vibrator aid. Neither the feature nor the spectral code was superior in aiding lipreading. The displays that produced quality changes seemed more efficient for training than the spatial display. Results were affected also by content and method of training and initial lipreading proficiency.