R.Are these two words pronounced differently?
The Collins Dictionary gives the following pronunciations.
But I don't think it's true. I think "shudder" is pronounced exactly like "shutter" - with an unvoiced /t/, or rather the flap, [ɾ]. My first question is if I'm right about it. I'm almost sure I'm right it is so in General American, but how about other accents?
I say 'shutter' with a [t] and 'shudder' with a [d]. It kind of makes sense! I don't see any need for learning how to produce flaps, taps, trills or clicks for learners of English. You can always slip into a dialect if you need to spend a period of time somewhere, but even then it's not necessary.
Another thing is that pronunciations in dictionaries are phonemic, so they use phonemes without any details. Maybe these are two phonemes realized with the same allophone? But that would contradict the definition of a phoneme, wouldn't it?
The flap [ɾ] is an allophone of /t/ in some American dialects. /ˈʃʌtə/ and /ˈʃʌɾə/ are the same word. I don't think there are any minimal pairs with [t] and [ɾ]. They are two allophones of the same phoneme, /t/.
The only justification for learning [ɾ] would be if they were different phonemes - if */ɾ/* and */t/* were different words. I don't think this happens anywhere.
(The same applies to glottal stops. /ˈʃʌtə/ and /ˈʃʌʔə/ are the same word.)