By American English, Allophones

Recently, because of my job requirements, I have to write some diplomatical letters to my business partners. For example, invitations, applogy for meeting postpone and so on. Sometime I confuse if I wrote perlite enough or If English speakers do use such sentences as I used to use in those...

I don't think it's called intonation. It's allophonic vowel length: vowel phonemes are realized as longer vowel allophones before voiced consonant phonemes in the coda of a syllable. This is found in all dialects of American English. Some American dialects have some phonemic vowel distinctions...

I'm not quite sure I understand your symbols. For one thing, North American English doesn't really distinguish vowel length, vowel phonemes are realized as long vowel allophones before voiced consonant phonemes in the coda of a syllable. Secondly, is the open front unrounded vowel

Allophones of /t/ in Standard American English I find these symbols the easiest to use without access to an IPA font. They also have the advantage that you can place them right into an English word to illustrate where they are used. (t'omato, stat'istics, wi.tness, bottom,...