HELP! what is that high pitched noise when tv is on?

[hollyro85]

Hello,
I hear this constant high pitched noise, almost like ringing, but even higher, from the tv. I can even hear it when i'm in another room.. i've become so familiar with the sound, I can tell when our neighbor turns his tv on, too. when the tv is not on, I hear a wave of the same pitch coming from the tv, and it only stops when I un-plug the tv. ANYONE know what's going on? Thanks..

 

[gregaaron89]

If it's a CRT tv, that's normal.

 

[minime72706]

Hello,
I hear this constant high pitched noise, almost like ringing, but even higher, from the tv. I can even hear it when i'm in another room.. i've become so familiar with the sound, I can tell when our neighbor turns his tv on, too. when the tv is not on, I hear a wave of the same pitch coming from the tv, and it only stops when I un-plug the tv. ANYONE know what's going on? Thanks..

I randomly came across this post on Google and figured I'd answer.
It's the vibrations of the flyback transformer that is responsible for the horizontal deflection of the electron beam that creates the picture. You can figure out the approximate frequency by thinking like this: There are 525 lines drawn on a television and the display refreshes at a frequency of (roughly) 60Hz (it's actually a very strange 59.94Hz) BUT REMEMBER THAT IT'S INTERLACED. This means that the signal that causes the horizontal deflection has to sweep across the 525 lines of the screen 30 times per second (half the image is drawn in an interlaced pattern at a time).
525*30 = 15.75kHz
This is why only some people can hear it. That's out of the hearing range for a large number of older adults.
Why do transformers vibrate? I won't go into that, but you'll be familiar with the problem if you've ever been near a device with "60Hz hum" that didn't come from a speaker. It's the power transformer vibrating at 60Hz.