ASA 127th Meeting M.I.T. 1994 June 6-10

4pSP11. Researchers beware: Use of speech-modulated noise adds strong ``bottom-up'' cues to phonemic restoration.

James A. Bashford, Jr.

Richard M. Warren

Chris A. Brown

Psychol. Dept., Univ. of Wisconsin---Milwaukee, Milwaukee, WI 53201

When deleted segments of speech are replaced by extraneous sound, the missing speech fragments may be perceptually restored and intelligibility improved. This phonemic restoration (PhR) effect has been used to measure various aspects of speech processing, with deleted portions of speech typically replaced by Gaussian noise. However, several recent studies [e.g., A. G. Samuel, J. Mem. Lang. 26, 36--56 (1987)] used noise that followed the amplitude envelope of the speech fragment, providing precise moment-by-moment control over the signal/noise ratio, but also possibly providing envelope cues concerning the replaced speech. The present study examined this possibility by comparing the effects of Gaussian noise and speech-modulated noise interrupters upon the restoration of intelligibility. Filling periodic interruptions in sentences with modulated noise produced twice the intelligibility increase obtained with Gaussian noise. Further, when isolated monosyllables were interrupted, interpolation of modulated noise increased intelligibility whereas Gaussian noise reduced intelligibility. It is suggested that, although the enhancement of intelligibility of speech-modulated noise is an interesting topic, the results obtained with the stimulus are confounded by the addition of bottom-up information not present when PhRs are produced by independent extraneous sounds. [Work supported by NIH.]