Lipreading sentences with vibrotactile vocoders: performance of normal-hearing and hearing-impaired subjects.
Three vibrotactile vocoders were compared in a training study involving several different speech perception tasks. Vocoders were: (1) the Central Institute for the Deaf version of the Queen's University vocoder, with 1/3-oct filter spacing and logarithmic output scaling (CIDLog) [Engebretson and O'Connell, IEEE Trans. Biomed. Eng. BME-33, 712-716 (1986)]; (2) the same vocoder with linear output scaling (CIDLin); and (3) the Gallaudet University vocoder designed with greater resolution in the second formant region, relative to the CID vocoders, and linear output scaling (GULin). Four normal-hearing subjects were assigned to either of two control groups, visual-only control and vocoder control, for which they received the CIDLog vocoder. Five normal-hearing and four hearing-impaired subjects were assigned to the linear vocoders. Results showed that the three vocoders provided equivalent information in word-initial and word-final tactile-only consonant identification. However, GULin was the only vocoder significantly effective in enhancing lipreading of isolated prerecorded sentences. Individual subject analyses showed significantly enhanced lipreading by the three normal-hearing and two hearing-impaired subjects who received the GULin vocoder. Over the entire training period of the experiment, the mean difference between aided and unaided lipreading of sentences by the GULin aided hearing-impaired subjects was approximately 6% words correct. Possible explanations for failure to confirm previous success with the CIDLog vocoder [Weisenberger et al., J. Acoust. Soc. Am. 86, 1764-1775 (1989)] are discussed.
Bernstein
L E
LE
Center for Auditory and Speech Sciences, Gallaudet University, Washington, DC 20002.
Demorest
M E
ME
Coulter
D C
DC
O'Connell
M P
MP
D000328:Adult; D003143:Communication Devices for People with Disabilities; D003638:Deafness; D005260:Female; D006801:Humans; D008085:Lipreading; D008297:Male; D011897:Random Allocation; D013067:Speech Perception; D014110:Touch; D014732:Vibration