You play with Cream? That's awesome! My band is "Skim Milk." We play light rock.
Air Bubbles on the Ceiling make a Rumble Sound that my Wife can't stand. My Wife and I were Cavern Diving Orange Grove and we were watching some Cave Divers come out from the shallow tunnel and our bubbles were moving on the ceiling making a noise that she felt uncomfortable.
Yeah, likely air. Now if you want to hear a real rumble check the Amtrak schedule and dive Edwards...