Ancient Chinese refers to Chinese from Shang Dynasty to Han Dynasty, and its pronunciation can be subdivided into pre-Qin phonology and Chinese phonology according to its evolution. Because the construction of ancient Chinese is not based on historical comparative linguistics, and because Chinese does not use pinyin characters, it is impossible to infer ancient pronunciation according to the "spelling" of different times. This principle is different from Indo-European.
The basic method of studying archaic sounds is to deduce archaic sounds from Middle Chinese.
On the basis of the medieval sound, we can infer the ancient sound by using the rhyme and sound system (pictophonetic characters) of The Book of Songs, and we can also use the ancient sound characteristics of Chinese dialects and some external evidence (Chinese cognates and loanwords in Chinese-Tibetan, Zhuang-Dong and Miao-Yao languages).