Loss of high frequency hearing with age is a well-known phenomenon. I was proud myself that I could still hear above 15 kHz at age 40, but eventually it got me too.
I don't know? I still remember the sound of CRTs, but I've not been around one in ages. Modern electronics are generally a lot quieter than CRT TVs, though, and it's the sort of white noise that I'd generally tune out if I do here it, I think? So I'm not entirely sure.
Certain light bulbs and electronics, but the biggest offender ime are power adapters. Check out bigclive on YouTube, he measured some standard USB to AC adapters and the noise they throw off is insane!!