While I agree with Ms. Sargeant's response, if it was me, I would also try to involve their landlord, the actual owner of that unit. It most likely is a breach of their lease to disturb their neighbors and if, after putting him on notice and allowing enough time for his compliance, the landlord still does not alleviate the problem, I would think about including him in the lawsuit. No landlord in their right mind is going to want to keep tenant's around who drag him into a lawsuit. Besides, to the extent you get a Judgment for damages, collecting from tenants may or may not be likely but you know the landlord has assets you can collect from. Go talk to a local landlord-tenant attorney.