Thanks for the topic... the UT definitely has a lot of holes. I believe the explanation of the UT (in-world) is that it would take the incoming voice signal, translate it (internally) and then deliver it in a close approximation of the speakers original voice (ENT? MAYBE TOS?. This does present several issues, mostly already pointed out. How about when there's multiple languages involved, how does each hear their own language? Why aren't many words (that aren't cusses) not translated when a person specifically refers to a term in their own language? Why don't we hear double speak (the untranslated and translated versions)? Even in human language translation there's a lot of difficulties as many concepts don't translate well, why isn't this more of an issue with other species, as it was with the Tamarians? How do they keep communicating when the translators are missing/fail (this bits inconsistent, as many times they can't).
I think they'd have to introduce an explanation of newer UTs... quite probably an inserted chip that's psychically based.
I think they'd have to introduce an explanation of newer UTs... quite probably an inserted chip that's psychically based.