General Question

xxporkxsodaxx's avatar

What's up with that sound from the TV?

Asked by xxporkxsodaxx (1386points) August 3rd, 2008

I don’t know about everyone else but I can here a high pitch sound or something when a tube TV is turned on. Like if my TV is on and someone walks in the room really quietly and I’m not even looking I can tell from the way the sound changes. What’s with that and does anyone else hear what I’m hearing?

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9 Answers

wilhel1812's avatar

Yeah, i hear it. i guess it’s some high frequency sounds that are just around the limits for what humans can hear. Not really an answer, but i do hear it.

jrpowell's avatar

Some info here.

marinelife's avatar

That does not seem to address the high-pitched part of the sound. Here are several possibilities:

“There are several parts inside the TV that can potentially make this noise. These include the horizontal flyback transformer, deflection yoke, other transformers, even ferrite beads in the horizontal deflection circuits. In addition, transformers or chokes in the switching power supply if this is distinct from the horizontal deflection circuitry. Or even a portion of the sheetmetal used for shielding if in close proximity to a magnetic component.

You have several options before resorting to a 12 pound hammer:

* As much as you would like to dunk the TV in sound deadening insulation, this should be avoided as it will interfere with with proper cooling. However, the interior of the entertainment center cabinet can be lined with a non-flammable sound absorbing material, perhaps acoustic ceiling tiles. Hopefully, not a lot of sound energy is coming from the front of the set.

* Move the TV out of a corner if that is where it is located – the corner will focus sound energy into the room.

* Anything soft like carpeting, drapes, etc. will do a good job of absorbing sound energy in this band.”

stratman37's avatar

@xxpork: Dang, good thing Marina wandered in! All I know about CRTs is that you CAN go to Heaven real quick if you touch the wrong thing inside. (move OVER Jesus, I’m trying to type here!)

syz's avatar

I’ve always read that women or more likely than men to hear flyback transformers, since women tend to hear higher pitches than men (sorry, I’m feeling too lazy to find the link). I am often unable to tolerate the noise in the electronics departments of stores. That whine drives me mad.

stratman37's avatar

and women call MEN dogs…

sndfreQ's avatar

In layman’s terms, what happens when the scanning takes place is similar to the function of “old school” typewriters. When typing one reached the edge of the page and has to hit the carriage return (where we get the “Return” key from on modern day computer keyboards). The carriage return advances the sheet one line down, and returns the position of the typewirter to the edge of the left margin.

In CRT type displays, an electron beam fires in the same manner across the screen; each time the ray advances down to the next line, there is an audible “click” made by the flyback transformer (?)...essentially as JP and Marina referenced, the rate of the “clicking” happens at approximately 15.5KHz, which is the frequency we hear when the volume is turned down. Actually in Europe and other countries that don’t go by the NTSC system (60 interlaced fields or 30 frames per second), the PAL system actually has a lower pitched whine (their CRTs only draw 50 interlaced fields or 25 frames per second).

marinelife's avatar

@syz You are correct about women’s hearing. There is supporting data in this thread.

Seesul's avatar

Do you think that has something to do with babies crying?

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