Has anyone ever heard (oxymoron surely?) real, proper, no-sound-but-those-your-body-is-making silence? This seems like a really strange question, but I ask it because I was standing on the edge of an estuary in Wales the other night and it was as quiet as anywhere I can remember being, no echoes, no noise, just the occasional birdcall and not much else...

Can you actually experience proper silence, or is there always (apart from your own body) something making noise?