Ken W. Grant
Louis D. Braida
Rebecca J. Renn
Res. Lab. of Electron., MIT, Cambridge, MA 02139
Many listeners with severe-to-profound hearing losses perceive only a
narrow band of low-frequency sounds and must rely on speechreading to
supplement the impoverished auditory signal in speech recognition. Previous
research with normal-hearing subjects [Grant et al., J. Exp. Psychol. 43A,
621--645 (1991)] demonstrated that speechreading was significantly improved
when supplemented by amplitude-envelope cues that were extracted from different
spectral regions of speech and presented as amplitude modulations of carriers
with frequencies at or below the speech band from which the envelope was
derived. This experiment assessed the benefit to speechreading derived from
pairs of such envelope cues presented simultaneously. In general, greater
improvements in speechreading scores were observed for pairs than for single
envelopes when the carrier signals were chosen appropriately. However,
lowpass-filtered speech provided at least as much benefit to speechreading as
any combination of envelope signals tested that had the same overall bandwidth.
Suggestions for improving the efficacy of frequency-lowered envelope cues for
hearing-impaired listeners are discussed. [Work supported by NIH Grants DC
00010 and DC 00117 to Massachusetts Institute of Technology, and by NIH Grant
DC 00792 to Walter Reed Army Medical Center.] [sup a)]Present address: Walter
Reed Med. Ctr., Army Audiol. and Speech Ctr., Washington, DC 20307-5001.