Aerobic blunder

I'm trying to keep my body moving because I spend so much time on my butt these days, with Greek flashcards or pages of Greek sentences to translate. So, I decided to do a little aerobic dance in my room, knowing that I have no roommates above me and (I thought) nothing in the basement below me. Imagine my surprise when, a couple of minutes into my wildly flailing about along with dBa's "3-D" from the bubble cd, I hear a knock on the door.

"Hi ... I'm from the offices beneath your room and all we can hear down there is BOOM ... BOOM ... BOOM ... BOOM ..."

Gak.