I know that the walls are not very soundproof e.g. I can hear Room 507’s television quite loudly in Room 506 (but do not worry about it because my mum has hearing problems and she cannot hear it.)
Even though the walls are not very soundproof, there are still solvable problems. For example:
1) with the previous noise problems, I could hear air-conditioners inside my room, but not outside my room (because these air-conditioners were far away). That seems to be completely solved by fitting the rubber mounts.
2) I expect it would be normal to hear air-conditioners from other nearby rooms, but the loudest should be from the room below (407) and the room above (605) - because they are the closest and they have a common wall with me. As I am quite sure that this is an air-conditioner noise, and you are sure it is not those two rooms making the noise, then there is something wrong with some other air-conditioner. (And that air-conditioner is nearby too because I can hear it outside as well as inside.)
3) we can ask tenants to put furniture protectors on the feet of their tables and chairs to prevent scraping noises. Etcetera.