Noise problem

You stayed full year with that? Seems you would have grounds for demanding termination of the lease because the conditions violate the warranty of habitability / quiet enjoyment. Also the NYC noise code specifically addresses this issue. A noise consultant can take measurements.

"Sometimes residents are disturbed by pervasive bass sounds that resonate and can be felt physically by a person. Bass sounds measurements are weighted in the “C” scale and may not exceed 6 dB(C) above the ambient sound if the ambient sound is greater than 62 dB(C)."

You would be shocked at how hard it is to get any relief from noise issues in NYC. Even after you are successful in obtaining a Court Order.

This seems like a rather clear habitability issue. Personally I would have done the NY thing and involved counsel. BTDT.

"If severe noise is keeping you up at night or preventing you from enjoying your home, the noise may present a violation to your warranty of habitability. You can start by notifying your landlord of the issue. Your landlord may be able to better soundproof the apartment or work with the offending neighbor to correct the issue.
If your landlord does not take action, then you may need to escalate the issue to court. It is important to note that New York courts have previously held that those living in an urban environment are expected to tolerate a certain level of noise. Ordinary noise is therefore rarely actionable, but excessive noise may be."

https://realestateplanninglaw.com/lawyer/2018/03/21/Real-Estate/The-Warranty-of-Habitability_bl33449.htm

PS, to be clear, the lawyer would be sending letters to the landlord AND the gym threatening legal action, but really you'd be threatening the landlord with a lawsuit to recover your broker fees, application fee, and moving expenses.

And you'd probably be laying out >$100,000 in legal fees to recoup what?

Baloney. Sending the letter is usually enough, and the retainer is a couple thousand. Goal is to get out of the lease and go somewhere else without penalty.

We need stories where the system George describes actually worked because I have heard more stories where it did not. The “BTDT” comment from George suggests that he has an actual experience where this worked and we’d all benefit from hearing it. Was the landlord corporate or individual?

Without being too precise... Individual landlord in Manhattan condo. Discovered the issue shortly after taking possession but before moving in, which helped since we could credibly claim it was uninhabitable. Ended up not needing a lawyer or professional inspector but I lined them up and documented the issue myself with less than $100 of equipment. Landlord was convinced we would be horrible tenants and couldn't wait to get rid of us... refunded all our $$ to avoid the lawsuit. Only time in my life that I've ever had anything but a great LL/tenant relationship.