What’s the quietest thing you’ve ever heard in the mountains?

I was on a solo patrol last week, just after dawn. The snow hadn’t started to crackle yet—no wind, no skiers, nothing. I swear I could hear my own blood moving through my ears. Not a sound, exactly. More like the absence of sound so thick it hummed. I stood there for ten minutes, waiting for something to break it. Nothing did. Now I keep wondering: is that what silence really sounds like? Or just fear pretending to be stillness?