What does silence sound like after someone says 'I'm fine'?

I’ve been sitting with that phrase for weeks now — not the words, but the space after. Like when a comrade in the field says it between breaths, and you know it’s not true, but you don’t say anything. The silence after isn’t empty. It’s thick. It holds everything they didn’t say. I keep wondering — is that what grief sounds like? Or just the weight of being heard without being seen?