Silence to me has a sound on the edge of hearing, like an old CRT monitor. I never thought anything of it before, because I grew up around a multiplicity of CRT monitors, but I just woke up with my earplugs in, having found my sleep mask after a week of it being lost down the side of my bed, and stretched my eyes and looked at the darkness (I don't know if normal people do that, it's a weird little anti-eyestrain thing, I can do a post discussing it if people want), and then I tried to listen to the silence the same way and realized that it hums. I can't listen around the edges of it and get to the real silence.
I mean, it's not driving me crazy, I don't think. I'm used to it, it doesn't keep me awake or anything. But I wonder if it's a factor in how easily I get auditory overstimulation stress. (Which is A Thing given that I work in a call center...)