To improve tone recognition in continuous speech, we propose a strategy focusing on separating regions influenced by tonal coarticulation from regions that more closely approximate canonical tone production. Given a syllable segmentation, this approach employs amplitude and pitch information to generate an improved sub-syllable segmentation and feature representation. This sub-syllable segmentation is derived from the convex hull of the amplitude-pitch plot. Our approach achieves a 15% improvement using our segmentation strategy over a simple time-only segmentation. Finally, a future extension with sequential labelling is discussed.