Acoustic encoding of vocally expressed confidence and doubt in Chinese bidialectics.

Language communicators use acoustic-phonetic cues to convey a variety of social information in the spoken language, and the learning of a second language affects speech production in a social setting. It remains unclear how speaking different dialects could affect the acoustic metrics underlying the intended communicative meanings. Nine Chinese Bayannur-Mandarin bidialectics produced single-digit numbers in statements of both Standard Mandarin and the Bayannur dialect with different levels of intended confidence. Fifteen listeners judged the intention presence and confidence level. Prosodically unmarked and marked stimuli exhibited significant differences in perceived intention. A higher intended level was perceived as more confident. The acoustic analysis revealed the segmental (third and fourth formants, center of gravity), suprasegmental (mean fundamental frequency, fundamental frequency range, duration), and source features (harmonic to noise ratio, cepstral peak prominence) can distinguish between confident and doubtful expressions. Most features also distinguished between dialect and Mandarin productions. Interactions on fourth formant and mean fundamental frequency suggested that speakers made greater use of acoustic parameters to encode confidence and doubt in the Bayannur dialect than in Mandarin. In machine learning experiments, the above-chance-level overall classification rates for confidence and doubt and the in-group advantage supported the dialect theory.