客語高元音 -u 及 -i 起首的零聲母音節，因強化音變使高元音逐步發展為濁擦音，合口字早於齊齒字發生音變。福佬客、畲話及閩南西片等閩客接觸的語言，受閩語塞音發達的特色牽引，高元音轉而發展為濁塞音。各種韻母有一定的演變次序，「音節成分的距離」為主要控制因素，音節中各成分分布越離散，音變就越早出現，而元音成分之間的距離比元音與輔音的距離更重要。第二控制因素則是「演變條件是否為音節中唯一的元音成分」，若演變條件為音節的響度高峰，音變將較晚出現。閩南西片方言因受到內部結構特性干擾，韻母的音變次序稍有不同。

In Hakka, the high vowels [u] and [i] after a zero-initial onset became voiced fricatives due to fortition. The sound change of [u] was earlier than that of [i]. High vowels became voiced stops because stops in Min are more active than fricatives. This occurred in dialects spoken where Hakka and Min had been in contact for a long period of time, such as Fulau Hakka 福佬客, She 畲, and West Southern Min 閩語西片. The rhymes changed in a particular order, depending on two factors. The primary factor was the distance between syllable components: The distance between vowels was more important than the distance between vowels and consonants. The other factor was whether the syllable consisted of only one vowel. Due to language-internal reasons, the order of sound change in West Southern Min rhymes was different from that of Hakka and She.