Never listen to white noise alone in the dead of night

I'm an acoustic architect. I was testing a top-of-the-line bone conduction monitoring headset, and at two am in the morning, I switched on full-spectrum reception. I expected to hear the sleeping breath of the city. Instead, what I heard was a sound coming from the ceiling directly above me — a scraping, like fingernails clawing desperately into concrete.

I assumed the upstairs neighbor was a lunatic. Until I pulled up the building's architectural blueprints, and what I found scared me.

There was no floor above me.