kroenen
Regimen Morum
However, we get a brief glimpse that there are people in the world that do actually speak, but these mutes can't understand them I guess because it is portrayed to us in gibberish sounds that are close to real language but not.
It's actually not gibberish. The man in the car speaks Esperanto, and he asks her the following:
He asks her if she is one of the survivors, if she is alone, why she is covered in blood, and if she is hungry. He proceeds to tell her that he lives at the end of the road and that there will be food for her there. He also asks her about the cross-shaped marking on her throat.