The tonal space of contrastive five level tones.

Multiple-level tone contrasts are typologically disfavoured because they violate the dispersion principles of maximizing perceptual distance and minimizing articulatory effort. This study investigates the tonal dispersion of a multiple-level tone system by exploring the cues used in producing and perceiving the five level tones of Black Miao. Both production and perception experiments show that non-modal phonations are very important cues for these tonal contrasts. Non-modal phonations significantly contribute to the dispersion of the five level tones in two ways: either by enhancing pitch contrasts or by providing an additional contrastive cue. Benefiting from more than one cue, the level tones T11, T33 and T55 are well distinguished in the tonal space; by contrast, the level tones T22 and T44, only contrasting in pitch, are the most confusable tones. The tonal registers model proposed in this article sheds light on the different uses of non-modal phonations across languages.