I live on the bottom floor of my apartment building. I have one neighbor across the hall from me who's always quiet, and one upstairs who is quiet at night.
I can hear a child thundering back and forth all day, and I am trying to do a major assignment for my grad program right now. All I hear is this child thumping up and down, running back and forth across the apartment, going out onto the balcony and banging on the railing, etc. Should I just listen to music? Should I try to confront them? Should I just lean out on my balcony next time I hear them and tell the kid to stop or to at least be quiet? I am getting close to my wit's end. It ain't cute. It happened last week and I thought they were moving furniture, but this is totally deliberate. Either that kid falls down a lot, or is just allowed to run wild all day in a small apartment. And yes, I've determined it's a child by the sound of a very annoying child voice.
ETA: I took the passive-aggressive way out. I played one song really loudly with my speakers, and now the noise has stopped (or at least abated)! I don't think it will last, but perhaps they realize that other people are here now? I hate confrontation, especially about children.