On some LCD monitors this will cause them to emit a tone (epilepsy warning) | Hacker News Reader

On some LCD monitors this will cause them to emit a tone (epilepsy warning)

thume.ca

148 points658166 comments

From another thread here: https://news.ycombinator.com/item?id=8856829

https://news.ycombinator.com/item?id=8857209

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.

In some humans this page will cause the head to ache.

My refrigerator's compressor just happened to turn on when I clicked the link. I was impressed.

It's similar to this image: https://i.imgur.com/Zihujue.jpg Try staring at that for a few seconds.

The best explanation is that it overloads the edge detectors in your brain. There are some other possible explanations here: https://www.reddit.com/r/explainlikeimfive/comments/1sgn7v/e...

Oh ya it does. For me, it's only when the bars get really bunched together... basically I can't stare at it anymore when it gets there.

Or cause a tonic-clonic seizure.

For me it causes faster breathing and faster (perceived?) heart beat..

I'm one of those humans. I helps not to look at the screen just listen and glance at it when you hear the tune.

good god man, my eyes, I can't feel my eyes!

Yes, I am one of those "some humans".

Any thought that this might damage our monitors?

Why is this downvoted, this is a very reasonable question.

Noise is a mechanical wave produced by something vibrating. If you can hear it, it means that thing is vibrating quite hard inside your monitor.

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.

More info: https://news.ycombinator.com/item?id=8856829

eli5?

https://news.ycombinator.com/item?id=8857209

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)

You're very right. Most electronics are from bad or undervolted caps.

The only thing to make sure is to put caps in the same polarity as the dead one (assuming polarity of said caps; some dont).

Can we get a warning on the link for people susceptible to epilepsy, seizures or migraines? Thanks.

I have added a warning; had to edit the title a bit though to stay under the 80 character limit.

also, no one knows if it can cause damage to hardware

If an image can cause damage to hardware we are in serious trouble with people out for the LULZ

https://news.ycombinator.com/item?id=8863041

LED noise is not due to something vibrating.

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.

LED noise is not due to something vibrating.

The definition of noise is, literally, something vibrating.

The definition of light is also vibrating aka waves :)

It is more likely to clear up lcd ghosting

a new angle on the good old 'can software damage hardware' question

I'm not crazy!

Some text patterns (like, say, grep going through minified JS) make my monitor emit a weird noise I was having all the trouble in the world believing.

Now I know this tone actually exists

As I was holding my iPhone up to my ear, I realized that there is a constant static noise coming out of my phone speaker, even with the volume down!

This page also produces a tiny bit of inductor noise near the middle of the device.

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 have a 2011 27" iMac and I can hear it, but it's on the edge of my perception.

I thought listening to CRT with AM radio was cooler, with Tempest for Eliza[0] :)

[0] http://www.erikyyy.de/tempest/

I've noticed this phenomenon before, then with the V File Viewer in CSV table mode until I changed its default colors.

This page did not seem to trigger it though.

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.

It would be fun to set this to a musical score, and run it on three monitors in harmony.

Also, for some reason the effect reminds me of this video: https://www.youtube.com/watch?v=Ht96HJ01SE4

I was hoping it was going to be musical and not just a rehash of the post from yesterday :(

It sounds like a circular saw. I guess certain sinusoidal patterns sound the same.

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.

I have a Dell 2407WFP and it made a sound, although I had to maximize it.

I had a Dell 2007FP rotated to portrait and didn't hear anything - rotated it back to landscape and I heard the sound.

Interesting. I have a Dell 2408WFP and it exhibits the behavior.

Dell E207WFP and it produces sound for the entire range.

You should try tinnitus, nothing is barely audible ;-)

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.

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.

Confirmed with LG 22MP65 IPS LED and iiyama ProLite E1906S.

You can hear a faint sound when the lines reach a certain distance from each other and it fades out as the distance changes.

Way cool, worked on my Dell U3011! How does this function, why does the screen emit a high pitched noise?

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.

27" iMac does indeed emit a tone.

Late 2009, 27" iMac: emits tone.

Nothing on mine, 2011 model.

I noticed this same effect with the Scroll Slow, Have Fun (scrollslowhavefun.com) demo from yesterday.

Can it damage those monitors?

My old Samsung's SyncMaster T200 sound a little at the thinner bars.

It does on mine (24" eIPS) at like 30% reduction.

Any chance of damage?

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)

Dell P2210 emits a tone. Motorola Moto G phone does not.

Can it be made to play 'Ode to Joy'?

Confirmed iiyama PL2779Q. Loud and clear

I think the tone is my eyes screaming.

This is some black mirrorish stuff here... I've suddenly forgotten who I am.

Long live the new flesh!

works here!

but could use a warning

I would think "on some LCD monitors this page will cause the screen to emit a tone" would count as a warning? :-D

What manufacturer / model?

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