Now that I'm middle-aged, I can tell there's a little loss around the vocal frequencies... but damn if those old tubes and pest devices aren't as annoying as ever. Ears are weird.
it looks my hearing drops off between 13k (noticeably quiet compared to 12k) to 14k (can't hear it at all).
The source of the sound is the transformer which resets the scan line back to the original side of monitor.
Last year I was in a mall where they had a Tesla store and it was emitting a horrible high pitched sound.
Where I live some houses have Seagull scaring devices and they also emit a horrible high pitched squeal which I'm guessing others can't hear, otherwise it would honestly drive you nuts.
Some malls do that deliberately to get rid of teenagers.