If people aren’t asking why you sound weird then you’re pronouncing them correctly. So you may not consciously recognize the difference using your ears, but in some way your brain and mouth know the difference.
A common minimal pair is “thigh” vs “thy”. The only difference (in common dialects) is the initial consonant (voiceless vs voiced).
That’s the only example of a voiced-unvoiced minimal pair I can find online. Presumably, due to the quirk of initial ‘th’ in English, pairs with the sound at the beginning will be hard to find, but there should be some with it elsewhere in the word.
Other examples I can think of:
“This’ll” (contraction of “this will”), and “thistle” (prickly plant)
“mother” (female parent) and “mother” (collector of moths), though those also differ in their first vowel sound
It’s funny how when you have H followed by U being pronounced as “ooo,” the “Y” sound inserts itself in the transition. But not when the U is used like in “hug.” You can intentionally leave it out, but then you get pronunciations like “hooman” instead of “Human.”
You also get that alteration (with some effects on the vowel) in pairs like bath / bathe and breath / breathe. I’ve always wondered why people misspell “breathe” all the time, but maybe it’s because they don’t fully perceive the difference between the two.
Ether/either is the only other minimal pair with the sounds in the middle of the word. Loath/loathe and maybe some others are at the end.
ETA: I thought I’d started a thread on this, but search fu is weak.
I think some people pronounce “thin” and “then” the same except for the unvoiced vs voiced th, though for many people it’s a different vowel sound.
The difference is either subtle or blatantly obvious, depending on one’s perspective. The argument for subtlety is that someone who pronounced “this”, “that”, “the”, etc with the unvoiced “th” sound would be perfectly comprehensible and indeed many people might not even notice. The “blatantly obvious” argument is that essentially all native English speakers produce the “th” sound of “this”, “that”, “the”, and so on, by producing the sound of the following vowel concurrently with the tongue-against-front-teeth fricative. For all other words beginning with “th” (thistle, theater, etc) there is no voicing – the “th” sound is made entirely by the breath, similar to the sibilant “s”.
Literacy has made us deaf to the sounds of our own language.