15.625KHz to be exact. I can hear this sound quite well, to the point where I prefer not to be in the same building as any CRT that emits it.
There are those that don't, mainly newer models I assume. I think it has to do with the exact shape of the waveform that drives the (horizontal part of the) deflection yoke. Some of them are noisier than others.
Same. As a child, I could be reading a book at one end of the house and I would experience discomfort (experienced as a slightly painful "pressure" in my ears) when the television, which was 4 rooms away, was powered on. My family didn't believe that I could tell, because to them it was silent. So they challenged me to a double blind test, and were surprised to find that yes, it really was the TV that was bothering me.
Related, we did a hearing range test in a high school science class. I could detect the tone generator at a frequency well beyond what anyone else in my class could pick up. I couldn't hear it as a sound anymore after a certain point, but could still feel it as an uncomfortable "pressure" inside my ears.
One of the power supplies I own makes a high-pitched whining sound from its fan. It's the most terrible, obnoxious sound, but I somehow don't mind it. It blends into the background after living in it for years. Still, when it goes away, there is nearly unparalleled silence.
There are those that don't, mainly newer models I assume. I think it has to do with the exact shape of the waveform that drives the (horizontal part of the) deflection yoke. Some of them are noisier than others.