What to do about tenant noise complaints?

[Julie Marquez]

Dealing with tenant complaints is my least favorite part of the property management gig, and this one is stumping me. Also, what vendor do I call to handle the noise complaints?!?

In a quiet fourplex building, upstairs lady is complaining about the noise being made by downstairs single lady. The noises are things like slamming closet doors and walking around (and things that sound like normal living to me), but they are happening in the middle of the night and keeping upstairs lady awake. I've been getting upset emails in the middle of the night for the past two months.

I talked to downstairs lady who is aware of the complaints and mentioned that she listens to her ipad loudly in the evening, but that's it. I guess I need to talk to her more and what - tell her she can't be awake in the middle of the night? Other people in the building don't hear anything. Do I need to go over there in the middle of the night to listen for noise to understand the issue? I'm at a loss on how to diagnose the issue and handle the people.

Both tenants are on month to month tenancy, so asking someone to leave is always on option, but they both pay their rent on time and cause no other issues. Any suggestions on how to handle these mysterious middle of the night noises?