You're hearing the flyback transformer vibrate. I could hear CRT TVs like that, but I haven't been around one in years.
In television sets, this high frequency is about 15 kilohertz (15.625 kHz for PAL, 15.734 kHz for NTSC), and vibrations from the transformer core caused by magnetostriction can often be heard as a high-pitched whine. [0]
In television sets, this high frequency is about 15 kilohertz (15.625 kHz for PAL, 15.734 kHz for NTSC), and vibrations from the transformer core caused by magnetostriction can often be heard as a high-pitched whine. [0]
[0] https://en.wikipedia.org/wiki/Flyback_transformer