Auditory supplements to speechreading: Combining amplitude envelope cues from different spectral regions of speech

Abstract

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 etal., 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.] a)Present address: Walter Reed Med. Ctr., Army Audiol. and Speech Ctr., Washington, DC 20307-5001.