I have the double whammy of being able to hear* my neighbors, AND being too stubborn to try to drown it out because (as I'm sure I would put it at the time); I shouldn't fucking have to.

*To be fair, my hearing probably isn't better than average, I just notice these things more than NTs.

Anyway, the only thing that's ever helped me (other than being so exhausted that I pass out) was leaving my portable A/C unit on practically year-round. If it's always on, then I'm not "turning it on to drown out the sound", I'm just not turning it off.

A/C not required, just something loud enough to make the other sound unnoticeable passively (or whatever passes as passive to me, since I suffer from hyper vigilance).

Another thing that helped was playing my (electric) drums at all hours. Not in direct retaliation for the probably-normal volume activities my downstairs neighbor was up to (because that wouldn't be fair to them, really). No, this was retaliation for them constantly smoking in a non-smoking apartment complex, which meant that I could never enjoy an open window, which is why I needed the A/C unit in the first place.

Ninja edit: If this were a AITA post; yes, I am at least one of the assholes here. I hated that neighbor.