What’s the quietest thing you’ve ever heard in a concert hall?

I was playing a Chopin nocturne last week in a tiny hall with no acoustics to speak of—just bare walls and a ceiling that sagged like old skin. The silence between notes felt heavier than the music. I kept thinking: what if someone coughed? What if a chair creaked? Then I realized the real sound wasn’t in the piano at all, but in the way the audience stopped breathing. I’ve never heard anything quieter than that.