I usually explain can vs can't as using a physics wave diagram. People can tell the difference in AmE because the waveform ends abruptly in 'can't' --- just as abruptly as if you pronounced the /t/ --- whereas in 'can' the word tapers off over a rather long period of time in the voiced nasal consonant.
In my answer to this question, I have been told by my English phonology and phonetics teacher who has an american accent or style, that the alviolar stop consonants sound [T], [P] and [K], which are unvoiced or voiceless, not to be spit (spat) when they are at the end of a word, just to made a slightly sound.
In regards to the word CAN and CAN'T, he also has taught me the following:
1) When CAN is at the end of a sentence has its full pronunciation or sound; as if it were isolated, for example:
Can you teach me how to dance?
Yes, I can. /kŠn/
I would like to go with you, but that depends if you can. /kŠn/
2) When CAN is not at the end of a sentence, the vowel ''A'' becomes Schwa /ə/
Can you go with me to the market Yulian? /kən/
I can go with you Carlos, but a little later. /kən/
3) About CAN'T, I have been taught the following:
a░ = In negative, the sounds remain strong and consequently do not change to Schwa sound.
b░) = The dental nasal consonant [N] is voiced and the alviolar stop consonant [T] is unvoiced or voiceless, so the voicing of the [N[ removes the unvoiced [T], but in this process the [T[ takes the voicing sound away from the [N] and let the [N] unvoiced, becoming the CAN'Tsound shorter than the normal. it sounds like CAN,but a little shorter.
c░) = Does this phonological phenomenon happen in British English (BrE)?
Last edited by The apprentice; 15-Oct-2013 at 06:39. Reason: editing