《中原音韻》的語音基礎是元朝的北方官話，周德清 (1277-1365) 特別將桓歡韻從寒山韻中獨立出來，是為了矯正當時的南方口音。元朝的南方官話或東南方言保留不少古音特色，現代江淮官話泰如片寒韻舌根、零聲母字讀 -ʊ 韻母顯示了中古《切韻》寒、桓不分的語音特徵，吳語、贛語也有平行表現。而山攝合口二等的「慣刪」、「環刪」、「篡刪」、「患刪」、「幻山」等字在江淮官話、吳語、贛語都有讀同桓韻的現象，這是早於《切韻》的語音層次。上述兩者不是元朝北方官話的音韻特徵，因此在《中原音韻》桓歡韻裡看不見這類的字音。總結來說，《中原音韻》桓歡韻在南方官話的演變途徑為：*uan > uõ > õ > ʊ。

The phonetic basis of Zhongyuan yinyun 中原音韻 is the northern Mandarin of the Yuan Dynasty. Zhou Deqing 周德清 (1277-1365) specially separated rhyme huan-huan 桓歡韻 from rhyme han-shan 寒山韻 in order to correct the Southern accent of the time. The Southern dialects of the Yuan Dynasty still retained many ancient phonetic features; for example, in the Lower Yangtze Mandarin Tai-Ru 泰如 region, words with velar and zero initials of the han rhyme are pronounced with -ʊ rhyme which shows that the han rhyme and huan rhyme are phonetically the same in Qieyun 切韻. Wu and Gan dialects also exhibit the same phonetic characteristics. The pronunciations of the words guan 慣, huan 環, cuan 篡, huan 患, and huan 幻 show that this feature existed earlier than Qieyun. Neither of these exists in northern Mandarin in the Yuan Dynasty. Therefore, such a phonological pattern is not visible in Zhongyuan yinyun. To sum up, the evolution of the rhyme huan-huan in southern Mandarin should be *uan > uõ > õ > ʊ.