Related: Is Kylo Ren's mask instrumented?
The answer to the above question mentions that Ren's helmet contains an "integrated vocabulator" that changes and projects his voice. But how does that component actually work? Is this simply a passive acoustic device or is it, say, battery-powered? We know the mask is not instrumented but that doesn't necessarily mean anything about the voice changer itself.
(I'm looking for the in-universe answer. Out-of-universe, I'm certain that it was an electronic effect used to dub over everything Adam Driver said while in costume.)