What are the durations of tones in Mandarin?
Do all tones have the same exact duration?
Other dialects can be noted as examples...
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Sign up to join this communityT1 = T4 < T2 < T3, which means that T2 and T3 are more complex tones.
https://naccl.osu.edu/sites/naccl.osu.edu/files/NACCL-23_1_06.pdf
My subjective view is that the first and third tones are quite long, and the fourth is short and abrupt. The paper by Chang cited in the other answer seems to confirm this:
[An] intrinsic durational difference among four Mandarin tones has been noted as early as in Lin (1965), with T3 being the longest, and T4 being the shortest. An acoustic study by Shen in 1990 confirmed T3 to be consistently longer than T2 when produced in isolation. (p. 86)
The part about isolation is important, though – it’s possible that lengths change in connected speech, and that how they change will shift depending on how fast the person is speaking. Incidentally, the Mandarin falling tone and the Thai falling tone both have a 51 contour, but they sound quite different, largely because the Mandarin tone is short and the Thai one is not (Thai also has vowel length as a contributing factor.)
In real world speeches and conversations you may want to adjust the duration of any specific character, either to make yourself comfortable or to show your stress.
However, the duration of tones is "undefined" in Chinese pronunciation system. As a native speaker, I have never been told that tones have exact or relative durations.
This doesn't conflict with the fact that in daily uses, characters with a specific tone may have a longer duration average. For example, the third tone is harder than others to pronounce, so you may want to spend a little more time on it if you are talking fast. But please note that duration is not a part of definition of tones.