To examine the time-varing manner on articulatory movement of the diphthongs, an investigation related to Chinese diphthongs is conducted by observing the durational distribution within these sounds in Standard Chinese. The preliminary results obtained here indicate that articulatory movement from one target towards another in diphthongs is not casual, but well-planned in time domain, and as the acoustic correlate, the time-varing manner of formant trajectories is determined by certain phonological and phonetic constraints of a language. Consequently, it is language-specific.

Keywords: diphthong, temporal distribution