Make sure there are no bugs, then there is nothing to reveal.

Why didn't YOU try to get out of the purchase? (Rhetorical question only). You need to talk to your RE or a real estate attorney about the noise issue and if it needs to be revealed. If you do something active, like schedule showings when you know the neighbors aren't noisy or are not home, then you'd have a liability issue for sure, not that anything comes of it. You could also happen to sell your unit to other noisy people that are inconsiderate jerks.

You might find it cheaper in the long run to have a professional sound blocking wall installed along the common wall. That, or call the police on the neighbors, or force them to move. Or sue them.