什么 (shénme) sounds to my ears more like (shéme).
Assuming I'm hearing correctly, is this just a common contraction of this word, or is the sequence "-n" + "m-" generally contracted to "-m-"?
Zhang and Yang (2007:157–165) classifies consonantal assimilation (輔音同化) in Mandarin into three types:
Examples of regressive assimilation
/n/ → [m] / _ [p pʰ m] (= all /n/ before [p], [pʰ], or [m] become [m]). All bilabial consonants in Mandarin exert an effect on an immediately preceding /n/. 什麼
naturally follows this rule.
Before | After | Pinyin | |
---|---|---|---|
麵包 | /mjɛn˥˩ paʊ˥˥/ | [mjɛm˥˩ paʊ˥˥] | miàn bāo |
亂跑 | /lwan˥˩ pʰaʊ˨˩˦/ | [lwam˥˩ pʰaʊ˨˩˦] | luàn pǎo |
難免 | /nan˧˥ mjɛn˨˩˦/ | [nam˧˥ mjɛn˨˩˦] | nán miǎn |
/n/ → [ŋ̟] / _ [k kʰ x]. I added the advanced diacritic for [ŋ] because Zhang and Yang claims the inherent nature of /n/ is still stronger than assimilation, so the result is not exactly velar. Also, notice in the first and third examples how the final has not changed from [aŋ] to [ɑŋ], so the result of assimilation is also not exactly ang in pinyin, either.
Before | After | Pinyin | |
---|---|---|---|
戰國 | /ʈ͡ʂan˥˩ kuɔ˧˥/ | [ʈ͡ʂaŋ̟˥˩ kuɔ˧˥] | Zhàn'guó |
辛苦 | /ɕɪn˥˥ kʰu˨˩˦/ | [ɕɪŋ̟˥˥ kʰu˨˩˦] | xīn kǔ |
山花 | /ʂan˥˥ xwa˥˥/ | [ʂaŋ̟˥˥ xwa˥˥] | shān huā |
/n/ → [ɲ] / _ [t͡ɕ t͡ɕʰ ɕ] (palatalisation before pinyin j q x), but /n/ → [ɳ] / _ [ʈ͡ʂ ʈ͡ʂʰ ʂ] (retroflexisation before pinyin zh ch sh). Personally I think these are less conspicuous.
Before | After | Pinyin | |
---|---|---|---|
班級 | /pan˥˥ t͡ɕi˧˥/ | [paɲ˥˥ t͡ɕi˧˥] | bān jí |
感情 | /kan˨˩ t͡ɕʰɪŋ˧˥/ | [kaɲ˨˩ t͡ɕʰɪŋ˧˥] | gǎn qíng |
看戲 | /kʰan˥˩ ɕi˥˩/ | [kʰaɲ˥˩ ɕi˥˩] | kàn xì |
班長 | /pan˥˥ ʈ͡ʂɑŋ˨˩˦/ | [paɳ˥˥ ʈ͡ʂɑŋ˨˩˦] | bān zhǎng |
難吃 | /nan˧˥ ʈ͡ʂʰɚ˥˥/ | [naɳ˧˥ ʈ͡ʂʰɚ˥˥] | nán chī |
天山 | /tʰjɛn˥˥ ʂan˥˥/ | [tʰjɛɳ˥˥ ʂan˥˥] | tiān shān |
Example of progressive assimilation
/∅/ → [ŋ] / [ŋ] _ (= all /∅/ after [ŋ] become [ŋ]).
Before | After | Pinyin | |
---|---|---|---|
嫦娥 | /ʈ͡ʂʰɑŋ˧˥ ɤ˧˥/ | [ʈ͡ʂʰɑŋ˧˥ ŋɤ˧˥] | Cháng'é |
Example of bidirectional assimilation
/n ∅/ → [ŋ̟ ŋ̟]. It is as if the third and fifth rules are combined.
Before | After | Pinyin | |
---|---|---|---|
專案 | /ʈ͡ʂwan˥˥ an˥˩/ | [ʈ͡ʂwaŋ̟˥˥ ŋ̟an˥˩] | zhuān àn |
天鵝 | /tʰjɛn˥˥ ɤ˧˥/ | [tʰjɛŋ̟˥˥ ŋ̟ɤ˧˥] | tiān é |
Reference: Zhang Bennan & Yang Ruowei (2007). [普通話連讀音變]. Hong Kong: Commercial Press.