Give them time to settle in. They are doing normal boar stuff and they are excited at having company and they feel safer in the dark when there are no humans/predators around at first. That is normal prey animal behaviour.

Please do not separate the cages.
Please read this illustrated guide here; it contains a lot of information on interactive behaviours and will help you to understand what is going on. You also may find the sound bite link helpful. It is one of the few that actually contains the correct interpretations. Boars always rumble when they meet; and babies are very vocal in their first months of life.
The problem with all these guides is that guinea pigs have a different hearing range, so we cannot hear (and differentiate) all the sounds they are making. Any sounds also comes with a situational context and body language. We need all three to get to the right interpretation. There are often two sounds that are very similar for us, but which can have very different meanings.
However, guinea pigs are great communicators, so you'll catch on fairly soon!
Illustrated Bonding / Dominance Behaviours And Dynamics
Guinea Pig Sounds