Abstract:
This study examined how signal degradation affects the use of natural formant transitions and following vowel quality (rounded versus unrounded) in the identification of a fricative noise continuum varying from /s/ to /sh/. The stimuli were made by combining a synthetic /s/-/sh/ continuum with vocalic segments extracted from natural tokens of /sa/, /sha/, /su/, and /shu/. These were presented in a clear condition and with the vocalic segment masked by signal-correlated noise at 1.8 dB SNR. Listeners labeled the fricative consonant that began each stimulus as ``s'' or ``sh.'' In general, the results replicated previous findings that /s/ transitions and the presence of /u/ gave rise to more ``s'' responses than /sh/ transitions or the vowel /a/ [V. A. Mann and B. H. Repp, Percept. Psychophys. 28, 213--228 (1980)]. It was further found that noise masking significantly decreased the effect of the transitions, but not the effect of vowel quality. Discussion of this interaction considers the effect of noise on (1) the salience of brief versus sustained speech cues and (2) the relative weighting of weak versus strong speech cues [Gordon et al., Cognit. Psychol. 25, 1--42 (1993)].