You guys are awesome. Thank you for the quick and helpful responses.

elmcannic: I think next step is to poll some folks to see if they hear any noises. Problem is I need to bump into my neighbors and I'm rarely home to be able to do that. Maybe I'll slip a note under their doors, hopefully that isn't creepy. It's a condo unit so they won't be able to relocate me unfortunately.

ABE: Building was constructed in 1979. This is the one in case it matters:
http://streeteasy.com/building/212-east-47-street-new_york

At this point, I'm putting the probability of my successfully convincing them to do something and that actually fixing the problem at 20%. And the odds of my growing used to the sound at 30%. So 50% chance this won't matter in a month!

Thanks again all.