Fourplex landlord needs help dealing with chronic noise violations

[Gregory R Ley]

In a fourplex, I have a tenant that is repeatedly loud with music, her 3 children, and guests as complained by all other tenants, to include after midnight into the early hours of the morning. This has been going on for 3 months. I've confronted her repeatedly, she stops, and two weeks later it begins again. One other tenant occasionally has loud noise as well, about every other month. The chronic offender complains about the occasional offender. How can I be equitable in my response and actions? Can I evict just the chronic offender? I installed NoiseAware in the common hallway, but convinced that it does not accurately record the volume. It reads 20 decibels when it clearly is much louder. Can I evict just on noise complaints? Although the statutes are clear in Minneapolis for the noise level violation, with out a calibrated instrument and a time stamp recording, isn't the complaint subjective? How can a landlord evict anyone without a documented event using calibrated equipment? I've never evicted anyone before. I'm scared that I will be leveled with discrimination. I've read the city and state statutes. I've called the attorney general and the city housing authority. They don't say anything helpful. I doubt I'm the first landlord to deal with this. Any help would be appretiated.