loud renters in my condo building

Hi there,

I have a question on what actions/rights I have with my situation. I am a condo owner in a 3 flat in Chicago for the past 7 years. The second condo unit owner on the 2nd floor has been renting out his place for a few years now. We never had an official vote, we were friends, and gave a verbal ok for him to do this. The latest renters are extremely noisy and we can hear the girl stomping around, slamming walls, etc and she is in the unit below us. we have never heard a noise from anyone before, so we know that this is extreme and a daily annoyance.

I have been sending about 10 emails to the owner, including detailed logs of the date/time/activity, he says he will call them, etc but I am spinning wheels here. She gets even worse knowing everyone in the building has complained.

Maybe filing a formal complaint somehow will get their attention? what is the process for this and do I have a chance? 

Thanks!