I'm sorry to hear you are dealing with this. I agree the neighbors should have told you directly. I hope you can manage to be quieter without being quite as nervous about it. Though I have to ask, do you think there is any possibility the manager is making this up to try to evict you for some other reason, perhaps to charge someone else higher rent? I just find it so strange that they don't want you to mention it to the neighbors, it almost seems fishy to me.