But do your lips ever become as round as when you say ü as a vowel (e.g. 玉 yù) or as a glide (e.g. 月 yuè)? Then they would have to unround a bit to pronounce the -ong.
The same question, asked in a different way: When there is no initial (e.g. 用 yòng), do you have the impression that you pronounce the same glide as in 月 yuè?
I think I would agree with Rethliopuks (#11) and tarlou (#21): It's something in between [j] and [ɥ] in terms of lip-rounding. Underlyingly, I would prefer to say that it's /i/ or /j/ (not /y/ or /ɥ/), with the rounding as an anticipatory phonetic effect, although historically I guess this was a case of unrounding.
When I pronounce xiong yong 汹涌, my lips are rounded through out the two syllables.
When I articulate xiong and yong, the xi and y part can be longer and I here a clear voiceless /y/ in xiong and voiced /y/ in yong. The x is also rounded before I make any audible sound (no matter it's voiceless or voiced sound)
I think there is no doubt that standard Mandarin yong has rounded medials.
Skatinginbc just wonder why Pinyin choose the symbol iong.
Although Skatinginbc seems to believe it's based on some phonetic facts.
I must disagree because:
1. Pinyin is far from a consistent system
2. Not only iong is arranged under 齐齿呼, ong is put under 开口呼 too. This is a systematic consideration, as I said in earlier post.
I used to think that it's just for consistency and convenience.
If we accept weng = ong, yu = ü, then it's reasonable to spell üong as either üeng or yong.
The latter is easy to write and type.
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One thing I don't understand is, why don't they just choose "ung" instead of "ong"?
Why not? Another person may ask why "ung" and not "ong".
3. Evidence from 王力's words.
王力《现代汉语语音分析中的几个问题》(中国语文1979年第四期, 王力语言学论文集314页, 王力文集第17卷)
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(一)汉语拼音方案委员会认为,在拼音方案中应该尽可能少用拉丁字母u,因为u在手写时容易和n相混。这样,“轰”的韵母本该是ung,写成了ong;“雍”的韵母本该是üng,写成了iong。合口呼变了开口呼了。我们讲四呼时,仍应把它们归入合口呼。“熬”的韵母本该是au,由于怕容易和“安”的韵母an相混,改写为ao;“腰”的韵母本该是iau,由于怕容易和“烟”的韵母ian相混,改写为iao。我们讲韵尾时,应该把这类韵尾认为是 u 。
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This not only clarified iong is rounded, but also answered my previous question: (if they have wanted to make a compact scheme,) why didn't they just choose ung?