Former Sound Engineer and well LEDs make noise (super quiet). My guess it is the transformer that is making the noise since a LED powered monitor is regulating the voltage of the LED as needed if it didn't do that your power use would be many times higher than with a voltage regulating transformer.
Wouldn't mean anything damaging is happening at all.
I have two Dell 2408WFP panels which didn't exhibit this behaviour. The older 2405 panel did (and the pitch changed as the bars narrowed and widened), although it was barely audible.
The most likely culprit is inductor windings. The magnet wire used for windings is generating a changing magnetic field which causes them to vibrate, usually at the fundamental frequency of the excitation signal. (see image at http://www.digikey.com/product-detail/en/744773122/732-1258-... for an example.) This is a fairly common source of audible noise in electronics.
Wish I could get it to work to check it out. I've tried with my 4k monitor, an HP laptop, and a macbook air, and just in case a galaxy S5 and I'm not getting anything.
TBH if your monitor would break due to a video signal I'd get a refund for supplying a sub-par product. Video signals shouldn't be able to break hardware (just people's brains according to some of the comments)
Interesting. My primary screen, a 27 inch Dell something-or-another costing me €350+ a couple years ago gives an audible noise at the thinner bars.
My secondary screen though, a Fujitsu Siemens 19 inch thing probably eight years old by now doesn't do a thing. However, that one broke down a couple of years ago - the condensators in that one had broken, and my dad replaced them with higher-voltage alternatives.
Note that monitors breaking down due to capacitor malfunction is a common issue - the manufacturers intentionally install capacitors with a too low voltage limit, which will cause the monitors to break down within 3-5 years, shortly after the required 3 years warranty. Planned / designed obsolescence, and stuff. Free business opportunity for anyone with a soldering iron: buy old 'broken' TFT screens and replace the broken capacitors with ones with higher voltages.
(note I'm not an electronic engineer and I forgot all of my education about the subject, my phrasing may be wrong)
There's a working theory in the Github explanation.
White and black pixels take different amounts of power to draw. As the screen scans up and down to draw the various rows, it thus has to rapidly charge and discharge the capacitors. The capacitors are expanding and contracting a bit as they do so, which vibrates the air and makes a tone.
Frankly this sounds like an awesome way to blow up those capacitors.
Nothing on my Retina MacBook Pro, Thunderbolt Display or 2011 27" iMac. Then again, I've got pretty bad ears. Now I need to send this to coworkers to see if their mileage varies.
I see that this screen has alternating black and white lines. I count 43 black lines on my monitor. Assuming 60 Hz refresh rate, that is 2580 Hz in terms of the pixels being off or on, which is a perfectly audible frequency. Even with 120 Hz refresh rate, that would be 5160 which is still easily audible. Without knowing anything else, I guess that there may be a capacitor somewhere that is charging and discharging along with the brightness of the screen as it is refreshed from top to bottom, which is causing it to flex in a way that produces an audible noise.
Works on a Dell U2713HM. The noise (well... at least the portion of the noise I'm capable of hearing) occurs when the bars are at their fattest. It's barely audible.
My LG W2242P does it for a range where the bars are at there thinnest. When they start getting close to thinnest, it gets higher pitched, and then reverses when they start to thicken again.
I'm somewhat relieved by this. I thought I had something wrong with one of my monitors. If I open a terminal window, make it cover most of the screen, and then view something with lots of long lines (such as Apache logs), I get a whining tone. It's bugged me for a long time not knowing what could be causing it.
This page also produces a tiny bit of inductor noise near the middle of the device.
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