Coding pitch differences in voiceless fricatives: Whispered relative to normal speech

Abstract

Intonation can be perceived in whispered speech despite the absence of the fundamental frequency. In the past, acoustic correlates of pitch in whisper have been sought in vowel content, but, recently, studies of normal speech demonstrated correlates of intonation in consonants as well. This study examined how consonants may contribute to the coding of intonation in whispered relative to normal speech. The acoustic characteristics of whispered, voiceless fricatives /s/ and /f/, produced at different pitch targets (low, mid, high), were investigated and compared to corresponding normal speech productions to assess if whisper contained secondary or compensatory pitch correlates. Furthermore, listener sensitivity to fricative cues to pitch in whisper was established, also relative to normal speech. Consistent with recent studies, acoustic correlates of whispered and normal speech fricatives systematically varied with pitch target. Comparable findings across speech modes showed that acoustic correlates were secondary. Discrimination of vowel-fricative-vowel stimuli was less accurate and slower in whispered than normal speech, which is attributed to differences in acoustic cues available. Perception of fricatives presented without their vowel contexts, however, revealed comparable processing speeds and response accuracies between speech modes, supporting the finding that within fricatives, acoustic correlates of pitch are similar across speech modes.