What’s the quietest thing you’ve ever heard a lock make?

I’ve spent years listening to locks—how they click, how they resist, how they surrender. But lately I’ve been wondering: what’s the sound of a lock that doesn’t want to be opened? Not the scrape of metal on metal, but something quieter. Like the hum of a door that remembers being closed. Or the breath between a key turning and the latch giving way. My dog hears it too—she stops mid-step, ears pricked, like she knows something’s not quite right. What’s the smallest sound you’ve ever noticed in a moment like that?