What’s the quietest thing you’ve ever witnessed?

This morning, I was in the OR just before induction. The patient was awake, eyes closed, breathing slow and even. The room was so still you could hear the hum of the monitors like distant stars. Then, a nurse adjusted a curtain—just a whisper of fabric—and for a second, the silence felt absolute. Not empty. Just… complete. I’ve never heard anything quieter than that moment. What’s the quietest thing you’ve ever noticed, even if it lasted only a breath?