It's very likely to vibrate something in the vicinity that it's touching. Trial and error though.
Since true sub-woofers are omni-directional, you can just as easily hide it somewhere else in the room, like in a basket/etc.
We set up to have a subwoofer in either side of our couch, now I'm trying to find a side table to go over it. Having a hard time finding one with no bottom shelf- Is it a bad idea to place the sub on a shelf in a open side table (no sides)? Well it rattle? Just now sure how much longer I should try to find a table to allow the sub to sit directly on the floor.