labiodental

These differences show , the labiodental phenomenon in the two localism areas not adjoined exist at the same time , not because of language shift by immigration , but because of the round lip nature and the fricative trend of head vowel .

这些差异显示，这两个并不相邻的方言区同时存在的唇齿音现象，不是移民造成的语言转移的结果，而是[u]介音的圆唇性质及其摩擦化倾向使这两个地区发生了同样的音变。

An Exploration of Round-mouth Characters of Zhi-system Read in Labiodental Sound in Shandong

山东知系合口字读唇齿音现象初探

The shifted of the sound changes phenomena in Shandong district proves that Round-mouth characters of Zhi-system read in labiodental firstly occur in fricative .

由这种音变现象在山东地区的地域流变情况可见，知系合口字的唇齿化有可能首先发生于擦音声母。