Abstract: A Fo-contour of syllibIes in Standard Chinese is generally divi-ded into the onset-curving segment, tone segment and offset-cur-ving segment. It is beneficial for teaching speech and developingspeech recognition and speech synthesis systems to investigate theconcrete location and relative length of the tone segment. The lo-cations of the tone segment on Fo-contour is determined on thewhole through a sequence of identification tests using two typesof the continua of synthetic stimuli. The perceptual center oftones(PCT)of a monosyllable, whether its initial is unvoiced or voicedand no matter which type of tone and the pitch range it has, islocated in the middle part of its final. So long as the length of thetone segment is about a half of that of the voiced part, the corres-ponding tones may be perceived.

Key words: speech perception, tone perception, the perceptual center of tones(PCT), tones in Standard Chinese