Very interesting and a hot topic for many of us, I'm sure. I've known for a while about regional differences (such as people in Shanghai not pronouncing the nasal final "-ng") but this is the first time I have seen it written that the vowel sound is also different in "pin" and "ping".

In the Zhuyin sound representation system the "~ing" of Pinyin is the combination of a symbol for a medial vowel sound i and another symbol for the final consonant "eng". So ping is written ㄆㄧㄥ (p + i + eng)

Maybe this is where the author (Olle Linge) got the idea for the hypothetical illustration of a "pieng" spelling.

Also an interesting discussion of "mental categories," which could also be an argument for learning Zhuyin.

I must admit that I don't hear any difference between the /i/ sound in 'pin' and the /i/ sound in 'ping' and I just looked at a few sources (including wikipedia) and they all write that the IPA for 'ping' is [pʰiŋ].

For me, I hear pYing, jYing etc. There's a Y sound in there.

@Podster: That's the way the sound is transcribed in IPA if you go into enough detail, there is an [ə] in there. However, as you say, this is reflected more clearly in Zhuyin. This is also true for some other sounds, actually, such as (Pinyin) "chun", which has the "-en" ending "visible" in Zhuyin, but not in Pinyin (where it would be "chuen").

@乖囡: Did you check the audio I referred to? As mentioned in the article, not all native speakers make the difference and not all make it clearly, but the two examples I linked to should be very clear. Regarding IPA, the reason you don't see the [ə] is because the transcription isn't narrow enough (or because you base your analysis on a speaker which doesn't pronounce it this way, of course).

@本杰明: I think that depends on what you mean by "a Y sound". If you mean as in "you" in English, this is not far from the truth. The "i" is often reduced to a [j] (often superscript, but can't write that here). This can also happen on syllables that doesn't have an initial, such as "ying" (so called zero onset).