Ah... that makes more sense, now
I talked to my roommate, Stefan, last night while I was washing dishes. I didn't say anything at first, but he started right in with, "Wasn't that SO cool!?" To which I had to reply, "It was... interesting. What was that?"
He says, "The banging and yelling and stuff? Today is the exact middle of the semester." Ah. He continued, illustrating on the wall, "The middle of the semester is hard. Everything before it gradually builds to the middle, then tapers off after."
Ah. Its a stress thing. The middle of the semester is the high-point of stress here, so they're releasing stress. Interesting.
another mystery solved!