Which tones are hardest, why, and where to start.
Korean speakers struggle most with Tone 3 (the dipping tone). The most frequent production error is producing Tone 3 as Tone 2. Their T2 and T3 f0 trajectories converge over time, whereas native Mandarin speakers' trajectories diverge toward the end of the syllable.
Source: Ko & Choi (2020), Phonetics and Speech Sciences 12(1), 11–17. DOI: 10.13064/ksss.2020.12.1.011 | Tu et al. (2016), Speech Prosody 2016, 375–379. DOI: 10.21437/speechprosody.2016-77 | Fu, Lee & Zheng (2025), Brain Sciences 16(1), 21. DOI: 10.3390/brainsci16010021
Group averages tell you where to look, not what you actually do. Two speakers of the same first language can differ a lot. The only way to know is to record yourself and compare.
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