American English: Gliding of the long "ee" sound: [i] to [ɪi]
I have noticed that Americans have (broadly speaking) two ways of pronouncing the long "ee" vowel as in "fleece".
A simple [i] that ends with the same quality it starts with: listen to user MinimalPairsChicago from Chicago
https://forvo.com/word/bean/#en_usa
[bi:n]A glide, (diphthong?) that starts from a position similar to the vowel in "bit": /ɪ/ and ends in /j/: listen to user falconfling from Texas
https://forvo.com/word/bean/#en_usa
[bɪjn]
I have found that people who pronounce the glided version (ɪj), also pronounce the simple vowel in other places: listen to falconfling say [tɹikəɫɪj]
https://forvo.com/word/treacly/
Also, the glided version occurs more often at the end of words, e.g.: "Danny", "really", but I haven't been able to hear it when it is fortis-clipped (before voiceless consonants like k,p,t and others). Also, when shouting, people usually glide the vowel.
My question is: How do Americans perceive this difference? Is one pronunciation more dramatic/educated/melodic than the other? Which accents tend to use which type of sound? Is there a more structured way of saying which sound is used depending on the environment (e.g. according to adjacent sounds)? Is there any research done on this?
What you are referring to is most likely what's referred to as a "Southern drawl" where those from the southern states in the US tend to speak a bit more slowly and draw out their vowels, which is what results in the glide as the initial emphasis behind the vowel (I forget how to describe this in phonetic terms) starts to diminish due to how long it's being pronounce. This may help better explain: https://www.quora.com/What-does-%E2%80%98southern-drawl%E2%80%99-mean