pǔ tōng huà / zhōng / de / chún chǐ / cā yīn / xū yào / ràng / qì liú / cóng / shàng chǐ / hé / xià chún / zhī jiān / tōng guò普通话中的唇齿擦音需要让气流从上齿和下唇之间通过。In Mandarin, a labiodental fricative requires air to pass between the upper teeth and lower lip.