If you are vocoding speech [with noise] then I’d recommend using a high-resolution vocoder , rather than audacity’s native vocoder, see … https://forum.audacityteam.org/t/how-to-make-vocal-like-burzum/38219/3
Now the bad news : the MDA talkbox high-resolution vocoder is not working with 2.1.1 version of Audacity, [ the last time it was working was in audacity 2.0.6 , I think ].