For the record, I don't own or know much about projectors...BUT!!...would it not be prudent to isolate the projector somehow with something like rubber pads/grommets/gasket kind of the way you might do to your speakers sitting on the floor. I realize this is caused by air pressure, but it still might help as well as firming up the supporting structure. Could it be the sound pressure acting on the floor beams....then to the projector?...maybe some pads might help to isolate it.

Half of communication is listening. You can't listen with your mouth.