"The distinction is in the pure vowel in Mxsmanic's dialect but it's the presence or absence of a diphthong in others."
Mind you, those dialects which use /e/ (as in "bay") in place of /eI/ or similar diphthong, are in the minority.
Minority: they still exist tho.
Cont.
These are the brain-dead transcribers who write "me" as /mi:/ reflecting the fact that it's both length and position which distingushes this vowel from /I/. Length is even phonemic in some dialects.
I am a colleague of Franz who asked the original question and am very interested in the answers as well. I guess, the difficulty that we have is that we come from German as our native language and are a bit confused as to the different transcription conventions in NAE. In German, there is no notion of a non-phonemic diphthong and something is either transcribed as diphthong (e.g. /OY/, /aU/, etc.) or it isn't. Thus, it seemed counterintuitive to transcribed "raise" as /rez/ when usually an /I/ can be heard. Of course, there are dialects where no /I/ can be heard, but suppose you want to design a speech synthesis system speaking the word "raise" which dialect would you give it? Most news anchors would probably pronounce the /I/ so shouldn't the synthesizer do so as well?
A similar issue exists with the Spanish place names. The "Los" in "Los Altos" should probably be pronounced like the English word "loss" rather than such that it rhymes with "nose". Yet, the transcription /los/ for "Los" can not distinguish from /noz/ for "nose".
Just to be clear, in English:
"loss" - /lOs/ or /lAs/
"Los" (Spanish article) - /los/
"nose" - /noz/
"Los" rhymes with neither "loss" nor "nose".
"Thus, it seemed counterintuitive to transcribed "raise" as /rez/ when usually an /I/ can be heard. Of course, there are dialects where no /I/ can be heard, but suppose you want to design a speech synthesis system speaking the word "raise" which dialect would you give it?"
In my experience, even those who transcribe it phonetically as a monophthong, themselves, regularly pronounce it as a diphthong, hence you usually hear the [I]. As Fred mentioned, this is particularly the case for words that don't terminate in a consonant. e.g. bay.
Pronouncing /e/ and /o/ as pure monophthongs is done in much of Britain (especially Scotland) and Ireland, and to some extent in the Upper Midwest.