I don't know how much this is evident, but the realm they're accessing doesn't have sound. So while Dominic can see the vibrations of their speech, he can't actually determine what they're saying. Cabal, having done this kind of reading since he was eight, has trained himself on how to interpret the vibrations and turn them into sound.

Seems like Cherlize is a quick study too... already able to understand the vibrations in the realm.