Kw. Grant et al., AUDITORY SUPPLEMENTS TO SPEECHREADING - COMBINING AMPLITUDE ENVELOPE CUES FROM DIFFERENT SPECTRAL REGIONS OF SPEECH, The Journal of the Acoustical Society of America, 95(2), 1994, pp. 1065-1073
Many listeners with severe-to-profound hearing losses perceive only a
narrow range of low-frequency sounds and must rely on speechreading to
supplement the impoverished auditory signal in speech recognition. Pr
evious research with normal-hearing subjects [Grant et al., J. Exp. Ps
ychol. 43A, 621-645 (1991)] demonstrated that speechreading was signif
icantly improved when supplemented by amplitude-envelope cues that wer
e extracted from various spectral regions of speech and presented as a
mplitude modulations of carriers with frequencies at or below the spee
ch band from which the envelope was derived. This experiment assessed
the benefit to speechreading provided by pairs of such envelope cues p
resented simultaneously. In general, greater improvements in speechrea
ding scores were observed for pairs than for single envelopes when the
carrier signals were chosen appropriately. However, when pairs of env
elope signals were transposed to low frequencies, the benefit to speec
hreading was no better than-the most effective single-band envelope si
gnal tested, or for a low-pass-filtered speech signal with the same ov
erall bandwidth. Suggestions for improving the efficacy of frequency-l
owered envelope cues for hearing-impaired listeners are discussed.