You can check your local municipal code about "noise complaints" (easiest way to do that is to start by calling your police department or the clerk of the town). Most cities/towns/etc. have rules about when you can make noise and maximum noise limits, and if the noise from the fans exceeds those limits or rules, you can file a municipal noise complaint against the downstairs owner.You can also check any rules governing your building and see if the level of noise of the fans, the disturbance of you, or the way the fans were installed violates the building's rules. If it does, you may be able to enforce those rules, though doing so would likely take a lawsuit if the condo association will not step in and help.Other than the above, there is little you can do: ceiling fans in a condo are highly unlikely to rise to the level of a "nuisance" in the law (this is generally reserved for uses inappropriate for the neighorhood, like a bar in a residential neighborhood playing loud music late at night), so if the building rules or municipal code will not help you, you may have to look to other solutions, like adding sound insulation or using white noise machines.