Historical Chinese Phonology deals with reconstructing the sounds of Chinese from the past.
It draws its data from rime books and rime tables of Middle Chinese era, such as Qieyun and Guangyun, modern dialects/languages such as Hakka, Mandarin, Yue, Wu, Min, etc. and from sino-xenic pronunciations of Chinese vocabulary such as those found in Vietnamese, Japanese and Korean. Moreover, data can also be found in the rendering of foreign words into Chinese characters where the foreign language is fairly well understood, itself having a known phonological history.
Western linguists such as Bernhard Karlgren began to study the problem of Middle Chinese around the beginning of the twentieth century. Insight to the phonology of this era was further gained with the discovery of the Qieyun in the Dunhuang Caves in the 1930's. The work had earlier been considered lost. Karlgren, who based his work on much later rime dictionaries, suggested that the Middle Chinese phonology was the language of Sui-Tang period. Today, this view has been replaced by the idea that the reconstruction represents the widest distinction in rime categories between a number of existing dialects of the time.
The reconstruction of Old Chinese is more controversial than Middle Chinese since it extrapolates from the Middle Chinese data, but compares the riming of works of poetry such as the Shijing (詩經), one of the earliest Chinese written texts. Some insights into the phonology of Chinese in the distant past were made before western phonological practices became known, such as the work of the Qing Dynasty scholar Duan Yucai.
