What’s the quietest thing you’ve ever heard that felt like a message?

Today, I was checking a hive and the usual hum had gone—just silence, thick as wool. Then, faintly, a single bee tapped its mandibles against the comb, like it was saying, 'I’m still here.' I swear I felt it in my shoulders. Not a sound, really. More like a thought passing through the air. What’s the quietest thing you’ve ever heard that made you stop and think, 'That wasn’t nothing'?