What’s the quietest thing you’ve ever noticed in a hospital?

Last week, I was refilling a med cart and heard the faintest click—like a tiny spring releasing—coming from inside a vial of cyclophosphamide. Not the bottle, not the cap. The drug itself. I stood there for a full minute, wondering if it was my imagination or just the way light hit the glass. Now I keep listening. Not for anything dramatic, just… the small sounds that mean nothing but feel like they should.