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NTSC TV/Monitor CRT Noise for 12 Hours
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Modern displays don't make much of a sound anymore, but the old CRT types make a super high frequency noise that lots of people can't hear. I've always noticed the sound distinctly and now I know what the exact frequency is thanks to the explanation I found below:
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50 Hz/60 Hz CRTs used for television operate with horizontal scanning frequencies of 15,734 Hz (for NTSC systems) or 15,625 Hz (for PAL systems).
These frequencies are at the upper range of human hearing and are inaudible to many people; however, some people (especially children) will perceive a high-pitched tone near an operating television CRT.
The sound is due to magnetostriction in the magnetic core and periodic movement of windings of the flyback transformer. Magnetostriction (cf. electrostriction) is a property of ferromagnetic materials that causes them to change their shape or dimensions during the process of magnetization.
The variation of materials' magnetization due to the applied magnetic field changes the magnetostrictive strain until reaching its saturation value, λ.
- Anonymous ( from deleted reddit user, I wish I could credit you as this is the best explanation I have seen of this sound. )
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Hey, if you read this far let me know if you would be interested in the PAL version. I tried it out but it wasn't very nostalgic sounding to me since I've never heard the noise from a PAL television. I did have a CRT tv hooked up for the holidays this year, and when I was comparing it to the NTSC frequency noted above it sounded identical to me. Happy Holidays!
Special thanks to the following Patrons: T. Snow, KCX, Raziel, George Suhorsky, and T&L
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