Abstract:

Sentences can retain intelligibility when heard through narrow spectral slits even though the fluctuating amplitude envelope within the narrow frequency bands contains little spectral information [K. R. Riener et al., J. Acoust. Soc. Am. 91, 2339(A) (1992); R. M. Warren et al., Percept. Psychophys. 57, 175--182 (1995)]. Other research has demonstrated that intelligibility is retained when broadband speech is divided into contiguous spectral regions and used to modulate the amplitude of corresponding regions of noise [R. V. Shannon et al., Science 270, 303--304 (1995)]. The current report combines aspects of these previous studies and provides information concerning the use of temporal pattern information in various regions of the spectrum: Two noncontiguous narrow bands of speech having various center frequencies were used separately to modulate the amplitude of noises, which were then refiltered to corresponding center frequencies and bandwidths. Despite the absence of spectral information within each of the narrow noise bands, listeners were able to identify many of the 500 keywords in the standard Central Institute for the Deaf sentences. It is concluded that intelligibility can be retained when acoustic information in sentences consists solely of amplitude changes occurring in two noncontiguous bands. [Work supported by NIH.]