I hear the exact same noise too. Fortunately it disappears when I stop thinking about it...........
We're surrounded by noise that we just naturally tune out. I live a half mile from a major six lane highway and when I go to bed, that's the only time I hear the traffic, but only briefly.
I grew up in northern Michigan and lived outside of town. I could go out in the back yard at night and when tuned into the surroundings, I could hear things creeping in the dead leaves, like worms and stuff. Pretty cool when you are focusing.......
And you have undamaged hearing.
It was back in the days of televisions with vertical and horizontal hold, and my grandma's bedroom was about two doors down. When the vertical hold went out of whack, she'd call me to fix it... she was already in bed.
Butg the curious thing was, I could HEAR when the vertical hold went out. The super-high-pitched whine of the TV would change. No one could hear it but me. They started to think I was psychic.
I used that fear to rule the household like some horrible Twilight Zone episode.