why can't my rats at least fight outside the supposed quiet times?

One day one of my neighbors is going to make a noise complaint about the infernal racket my current rats produce when they squabble. They aren't injuring each other with more than some surface scratches and bites (mostly it's just flying fur), but they are squeaking at a volume that is incredible. Seriously, most of my previous rats didn't fight with squeaks this loud. They are almost as loud as fighting cats. And of course they are banging against the metal sides of their cage, both with their bodies, and slamming parts of the cage interior that are hung up, like tubes and branches, around. So there are loud clanging noises. All in the middle of the night. At least the fights don't last long, but still.