I would like know which consonants are aspirated in American English and when? Also, when are they not aspirated?
I'm American, but not an expert on American pronunciation. I would say
- 't' is always aspirated at the start of a stressed syllable: tall.
- 't' is never aspirated at the end of an unstressed syllable: rabbit.
- 't' is never aspirated after an 's' when they start a syllable: store, strike.
I believe that in most other positions, several factors determine the aspiration of the 't' (which words are emphasized, which sound follows a 't' at the end of a syllable, and the speaker's dialect.)