I'm 33, I got a powerline plug that emits a high-pitched whine that drives me crazy. When I was in Tokyo, my friends and I would pass outside a shop at night that would have a supremely annoying whine that made me quickly walk away from it, but none of my friends could hear it.

I also frequently have to ask people to repeat themselves and can't hear what they're saying well in noisy environments. I think I have superhuman hearing loss.

There are shops in Tokyo (and other countries) that emit a high pitched noise to keep teenagers from loitering

I'm in Osaka right now and you'll find those around the temples at night. They kill my ears but I'm the only one in my group that can hear them.

I think they're meant to scare cats away, but they work well for teenagers and people like myself (26)

While I don't think we have those, there are anti-marten devices for cars that are supposedly outside of the range of human hearing. They really hurt.

When I was a kid, we had a monitor that whined when there wasn't any video going to it. My parents couldn't hear it, but I could hear it from across the house. I'd get up when my father went to bed to turn it off.

Closer to what I think you're describing: The TV didn't "whine" really (at least, I was never completely conscious of it), but I always knew when it was on.

My hearing isn't quite as good now, but there are still a few devices that I keep unplugged because they're loud and high-pitched.

With an app like Spectral Audio, you can actually prove this to them. Though informing them of their inferior hearing may not be beneficial to a friendship. Ymmv.

I was 26 before I realized the whole world couldn't hear CRT screens.

I find that hard to believe (that the whole world can't hear CRT screens) as the capacitor or whatever it was, winds up/down - it's pretty loud. I think it's the case that there are a lot of older people that can't hear that high pitched scream, and its only younger people who can hear in that high frequency.