The sound a train yard makes after the last engine is cut

I've been sitting in the cab after finishing up, just listening. There's a valve that bleeds off pressure for a good twenty minutes after shutdown—a low hiss like something exhaling. The rails ping as they cool. Nobody talks about this part of the job, the quiet that comes after the noise. Feels like the yard is breathing, or remembering. That's what I'm showing today: not a thing I built, but a thing I noticed.