Conclusions: Training protocols for learning non-native vowels should present a full set of vowels and should not focus only on the more difficult vowels.

总之，对于非母语元音学习的训练方案应呈现全套元音，而不应只集中于相对复杂的元音。

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However, research on perception training for non-native vowels is still scarce, and none of the previous vowel studies trained more than 5 vowels.

然而，迄今为止针对非母语元音感知训练的研究仍然很少，以前的元音研究中元音训练都不超过5个。

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