第三，本文结合语音学和历史音韵学理论，讨论了导致语音变化和内部差异产生的原因。

Utilizing the theory of phonetics and historical phonology, the thesis discusses the cause of the sound changes and the diversities.

youdao

林先生认为，现代语音学的历史可以分成五个阶段；

Prof. Lin claims that the history of modern phonetics can be divided into five stages;

youdao

林先生认为，现代语音学的历史可以分成五个阶段；

Prof. Lin claims that the history of modern phonetics can be divided into five stages;

youdao