What I’ve come to realize is don’t say you have thin floors. As long as your building is up to code your floors are fine.
Floors, squeak, and make noise no matter the age.
Explain that noises from the floor, occasional banging, walking, phone conversations are normal apartment living noises. Compare it to a house where there are shared walls.
Explain that sharing walls as part of apartment, living. Go on to say that noises such as screaming, loud music after a certain time, loud parties, excessive banging for over in 10 minutes, is unreasonable.
If noise levels are considered unreasonable, and it’s during office hours, tell him to call the office. Let you guys handle it from there. If after office hours, they will need to call the police.
Explain that you cannot guarantee quiet because there are shared walls. Explain that their neighbors most likely are hearing them too.
Reiterate what is beyond reasonable