拓跋氏於西元四九五年詔示斷北語、 接受並運用漢字漢語為統治漢人的溝通工具。 此漢化政策促成一個大規模的強使突厥語人學習漢語的局面、從事第二語言習得（second language acquisition 或簡稱 SLA）。此項 SLA 把「突厥方音」引進漢字語音系統。
　　這 SLA 事件、事實上是研究聲韻學的盲點。揭開此盲點、我們可以合理的解釋切韻系統的一些二元對立共存的現象、例如古今、南北、輕重、專出己意及祖述舊音等等、乃突厥語人從事 SLA 必然產生的中介音系的體現。藉此、韻鏡的雙重性格：共時性和歷時性，得明確的突顯。清儒的古音部和次第相連的韻鏡圖號有密切的關係。
　　我們發現古本聲類有十八、因拓跋氏的參與而衍生成今變聲的四十八類。也因為拓跋氏的參與、吾人可認定韻鏡的四十三圖實可朔源自古韻鏡十一圖。
　　廣韻忠實地保存著第五世紀前的反切舊文。因此、廣韻呈現許多上字反切類隔的現象。類隔是反應舊文反切的事實。
　　韻鏡系統（包括韻鏡及七音略）的 “輕重” 標記，忠實地記錄著、突厥官員習得漢語時的中介語音。韻鏡系統中標 “輕” 的韻圖、羅列漢字古本韻。而標 “重” 者、則展示帶著突厥方音的韻類。

　　In a royal edict of 493 CE, the emperor of the Northern Wei promulgated a sweeping sinification program, among which was the policy to forsake the northern language code-named duanbeiyu (斷北語). This language policy effectively required all Northern Wei government officials to take up the Chinese writing system and spoken language to conduct the business of governance over the majority Chinesespeaking subjects. It engaged the Turkic-speaking government officials to study Chinese and emulate pronunciations of Chinese characters, amounting to a large-scale adult second language acquisition (SLA) project. Modern scholarship on SLA revealed that adult second language acquisition seldom achieves its intended goal and ultimately it attains an interlanguage stage. Northern Wei officials, in their SLA project, had created the Turkic lect (TL) (突厥方音) with written Chinese as the model code (MC) (漢字本音).
　　Via Turkic imperatives for fortis/lenis opposition and backness/frontness opposition, Tabghatch sinification managed to make the classical 18-onset-phoneme system proliferate into a 48-onset system of the post-5th-century eras. The 18-onsetphoneme system is the model code (MC) that Tabghatch government officials tried to emulate. The 30 new onset sounds that resulted from the emulation process is the Turkic lect (TL).
　　As a repository of all pre-5th-century traditional fanqie spellings, Guangyun (廣韻) contains the records of the competing MC and TL manifested as incongruencies in onset fanqie spellings (類隔反切). The sound change induced by sinification also makes the eleven native rhyme charts (古韻十一圖) split into the forty-three charts of medieval Yunjing (韻鏡四十三圖), exhibiting eclectic dichotomy in MC and TL rhymes, labeled as light and heavy (輕重) respectively.

拓跋氏漢化; 漢語本音; 突厥方音; 古本聲韻; 今變聲韻

Turkic sinification; model code; Turkic lect; Guangyun; Yunjing