People who live in areas associated with a given accent (southern drawl is a good example; so is the classic Brooklyn accent) are not unable to hear the sounds they are making.
A phonics teacher addressing a linguistics course in New York: ::writes “Aww poor baby” on the board:: Up here in this part of the country we render this as
ɔ pɔr bebi
That typical nju yɔk aww sound is actually a pure vowel, although not one that’s often found pretty. If you go to other parts of the country, Alabama let’s say, you’ll find that words written with “aw” or “au” or “ou” are generally rendered with a diphthong. ::writes the IPA for Aww poor baby as it would be pronounced in Alabama::
ɑɔ pɔr bebi
A conversation in northeast Georgia: “Say ‘lawyer’. Yeah, see, you yankees make it rhyme with ‘more yer’ (lɔr yɚ). Down here we say it more like this: lɑɔ yɚ”
It’s not that people with a “drawl” can’t tell, it’s that they don’t consider their way of talking to be wrong!