Neighbor keep complaining about my tenants

[Nicoló Tossici]

It is few days now that a woman that lived in the condo below mine, is complaining because my tenants walk in the condo loudly. I do not know what to do. To be kind I went to speak with her and I gave her my number, now she is calling me every night. Moreover she goes to knock the door of my tenants every night and they are starting to get pissed of this. What should I do? Should I talk with the condominium association or not? At this point I do not even know what to think. I do not know if is true that my tenants are loud or if this woman just complain for everything. I think is normal to listen the step of the people living above you. 

Thank you