If the universal translator works the way it's said to, then everyone would still look like they're speaking whatever language they're speaking
But the thing is, there is no official "way it's said to". No onscreen source has described the principle of operation yet.
A simple explanation presents itself, IMHO: the UT does not consist of a microphone/computer/loudspeaker combo, but rather consists of an ear/computer/brain combo. That is, the UT intercepts the neural output of our ears, translates that, and feeds it onwards to our brains; possibly it also intercepts the neural output of our eyes, translates that, and feeds it onwards to our brains.
Thus, we hear the alien language; the computer in the UT translates that, and fools our brains into thinking that the translation is what we heard; and then our brain accepts that translation as if it had been spoken by those alien lips. At which point the brain, clever and practical as it is, either fools itself into thinking that the lips are in synch - or is fed a translated lip movement sensation by the UT.
The important thing to realize is that the camera is also equipped with the UT. We're not some 21st century, UT-less people sitting in the same room with these future people who have UTs. We're UT-equipped people ourselves.
If it can suss meaning from the brain's electromagnetic signals, that's not translation, it's telepathy.
Bullshit. Neural EM signals are no more "supernatural" than sound waves. There's no fundamental difference there; in fact, neural signals probably have less noise and less ambiguity than audio signals. To say that the UT couldn't translate brain signals is akin to saying that it couldn't translate the electrical impulses coming from a microphone!
In the episode The 37s, Janeway indicated that the translator was in the combadge.
It's probably both there AND in a brain implant. In "Basics", removal of the badges means our heroes cannot learn new languages (such as that of the natives on the volcano planet), but they can still understand alien languages the UT has already familiarized itself with: Janeway, Kes, Neelix and Culluhall understand each other without the badges.
So the badge is probably just a booster processor for assimilating new languages, and the implants handle a preprogrammed set of languages in all conditions.
Timo Saloniemi