Tone perception has drawn much attention in recent years. However, previous studies have mainly focused on tones with different contours, while systematic investigation of tones with the same contour—particularly falling tones—remains scarce. Given that different tone contours may elicit distinct perceptual patterns, examining tones with the same contour is crucial for understanding how listeners distinguish closely related tonal categories. Taking the four falling tones in Bai (Meiba variety) as an example, this study first demonstrates the acoustic foundation of these tones using acoustic analysis. On this basis, the perceptual experiment reveals that identification of these four falling tones shows gradient boundaries and no sharp discrimination peaks, a pattern often described as continuous perception in previous literature. Moreover, the phonation types of tones also affect the identification score and boundary position. Based on the systematic relationship between phonation types and perceptual measures (i.e., identification score and boundary position), this study proposes an operational criterion to identify whether the phonation types of speech sounds are the same.
Liu et al. (Tue,) studied this question.