SPEECHREADING SENTENCES WITH SINGLE-CHANNEL VIBROTACTILE PRESENTATION OF VOICE FUNDAMENTAL-FREQUENCY

The main goal of this study was to investigate the efficacy of four vibrotactile speechreading supplements. Three supplements provided single-channel encodings of fundamental frequency (FO). Two encodings involved scaling and shifting glottal pulses to pulse rate ranges suited to tactual sensing capabilities; the third transformed F0 to differential amplitude of two fixed-frequency sinewaves. The fourth supplement added to one of the F0 encodings a second vibrator indicating high-frequency speech energy. A second goal was to develop improved methods for experimental control. Therefore, a sentence corpus was recorded on videodisc using two talkers whose speech was captured by video, microphone, and electroglottograph. Other experimental control issues included use of visual-alone control subjects, a multiple-baseline, single-subject design replicated for each of 15 normal-hearing subjects, sentence and syllable pre-and post-tests balanced for difficulty, and a speechreading screening test for subject selection. Across 17 h of treatment and 5 h of visual-alone baseline testing, each subject performed open-set sentence identification. Covariance analyses showed that the single-channel supplements provided a small but significant benefit, whereas the two-channel supplement was not effective. All subjects improved in visual-alone speechreading and maintained individual differences across the experiment. Vibrotactile benefit did not depend on speechreading ability. PACS numbers: 43.71.Ma, 43.71.Es, 43.66.Wv. © 1990, Acoustical Society of America. All rights reserved.