...is a neighbor who constantly plays music that's just loud enough for you to hear, but not enough to tell what the fuck it is. All I know is, it's either the same damn song over and over and over again, or a series of songs that have remarkably similar basslines. Slow, monotonous basslines.
Actually, any repeated sound is that much worse if you can't quite tell what it is. In my old place, the people in the apartment right above me used to, frequently, do...something...that I could only guess was a really lively game of marbles. Or, possibly, they had a barrel of ball-bearings rigged to a trip-wire so that every time someone got up to go to the bathroom or something it spilled all over the floor...and then, they had to recollect the whole thing, one. click. at. a. time. Favorite time of day to do this: one or two in the morning. Or there was the next-door neighbor who was training to be on Broadway: never could quite make out which showtune it was, but whatever it was, it was always heartfelt.
Ahhhh, apartment living. Did I mention the part about what the fuck am I doing here, in New York, with the extra-big-buildings-with-their-very-old-and-thinning-walls, among other things? I may have, once or twice, of late.