My upstairs neighbors are LOUD AS HELL. Like, amazingly loud. We cannot figure out what they're doing up there either. My SO woke up the other night to some repetitive banging at 4am. These people have a ~6month old baby and a dog, but it sounds like they are constantly pounding on the floor. We have done everything from leaving them a note, knocking on their door (we can hear them up there but they refuse to come to the door) and occasionally, my roommate will bang on the ceiling when it gets really out of control. We spoke to the apartment manager and she just said, "It never occurred to me. We don't hear you." (They live under us.) I'm at a loss, but it honestly sounds like The Hulk is up there throwing furniture around.