Yeah, I’ve got that tunnel on my list. I logged a low‑frequency hum there that pops up when the night shift runs the old ventilation system. It’s more like a 50‑Hz buzz than a ghostly choir, but it does sound kinda alien if you’re standing still. I’ve got the tape and the paint scrap notes, just in case it turns out to be a hidden transformer or an old boiler cycle. Keep your ear peeled—urban ghosts love to ride the subway lines and the echo of old pipes.