Perception of Tone in Whispered Mandarin Sentences: The Case for Singapore Mandarin

Whispering is commonly used when one needs to speak softly (for instance, in a library). Whispered speech mainly differs from neutral speech in that voicing, and thus its acoustic correlate F0, is absent. It is well known that in tonal languages such as Mandarin, tone identity is primarily conveyed by the F0 contour. Previous works also suggest that secondary correlates are both consistent and sufficient to convey Mandarin tone in whisper. However, these results are focused on Standard Mandarin spoken in Mainland China and have only been obtained via small-scale experiments using citation-form speech. To investigate whether these results will carry over to continuous sentences in other variations of Mandarin, we present a study that is the first of its nature to explore native Singapore Mandarin. Unlike related works, our large-scale perceptual experiment thoroughly investigates lexical tones in whispered and neutral Mandarin by involving more diverse speech data, greater number of listeners and use syllables excised from continuous speech to better simulate natural speech conditions. Our findings differ significantly from earlier works in terms of the recognition patterns observed. We present further in-depth analysis on how various phonetic characteristics (vowel contexts, place and manner of articulation) affect whispered tone perception.