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This somehow manages my monitor to make a high pitched sound. It's an LCD monitor. It's the actual monitor making the sound. Switching to a different window or tab makes the sound top. Taking a screenshot of the tab, and closing the tab but viewing the screenshot, produces the sound.

"Some surface-mount capacitors exhibit acoustic noise when operated at frequencies in the audio range." [1]

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.

I am curious is Aardwolf can produce different frequencies by varying the width (and therefore the quantity) of black and white lines on the screen. If so, you should be able to play some music on it.

[1] http://www.edn.com/design/components-and-packaging/4364020/R...

I mocked up a quick JS canvas page that varies the bar width and I do indeed hear the tone changing:


I also put some ideas on the Github Readme including using feedback from the microphone to calibrate a width->pitch mapping to play music using your screen.

Hey, I forked your repo and added tuning, so that everyone can adjust it for their display


Maybe I'll get to get it play music (a json with timings and notes would suffice, I suppose?)

You shouldn't even need the microphone. Assuming that doubling the line frequency doubles the audio frequency, you can play music by just choosing a note to call "A" and varying the frequency from there. It won't be in tune, but that doesn't really matter.

Hey, I have done some work on my fork, and now it plays NYAN CAT (didn't have any better idea...)


You have to calibrate it before it starts playing.

I can hear the result of this, but it's barely audible, and only near the top of the range, at bar widths thinner than the OP.

I'll have to find some other monitors to test this on. It would be awesome if there were some commplace model that's relatively loud for a wide pitch range. Said model might then be useful for musical hacks in the same vein as driving the stepper motors in old floppy drives.

Please make a Show HN post. Also prepare for a lot of hits from the random internet. This is amazing.

Hey! For me, this produces sound for the whole range of heights/frequencies! It plays a bit more silent for high frequencies, but for the lowest ones, the sound is quite loud (given it's produced by a screen...) and I think, it could easily go for an even lower pitch. I am using a modified SyncMaster 203B (I replaced some of the electrolytic capacitors after the lighting ceased to work, so that may be it...)

My monitor plays the whole range as well, that's what I calibrated the height sweep to.

Neat. I don't notice anything/much for most of the cycle, but somewhere in the middle I can hear a brief "zwip" rising tone, for part of a second. I happen to have three "identical" monitors, and it's similar on each one, although I believe I can hear the tone for a somewhat longer range on one of them.

I can verify that I hear noise from this on my Macbook Air, faintly, and it also creates a buzzing sound on my iPhone 5s!

I'm on a Macbook Pro. Can't hear anything. Sad :(

Also on an older iPad

I enjoyed that. no noise on my chromebook will try on big monitor in the morning.

That's so cool! I can hear it on my Nexus 5 if I put it right up to my ear!

Awesome! I can hear it perfectly on one monitor at home, but not the other.

This is amazing. Yes, add a song or I will.

If so, you should be able to play some music on it.

Also makes for a nice covert channel... similar tricks with "listening" to the noises a computer makes have been shown to be possible to use for extracting information like encryption keys:


Inductors do this as well. The changing magnetic field causes the windings to vibrate, creating an audible sound. The sound my work monitor makes sounds like an inductor to me.

Right--or more commonly the cores of old power transformers will softly buzz at 60 hz.

You'll find it a lot in switching DC-DC converters as well. The pass inductors that help filter out the switching frequency can make quite a bit of noise, especially at higher loads.

My dimmable touch lamp makes an annoying high-pitched sound that is loudest on the dimmest mode. I searched for an explanation and apparently some light bulbs have filaments that are flimsy or light-weight enough that they vibrate audibly.

The power supply on the old Apple II "chirped" when switched off. I always understood it to be the oscillator decaying down from 20 KHz to DC in half a second or so.

Zooming in and out does produce different audible frequencies on my screen.

Something quite different, but it reminds me of Tempest for eliza: http://www.erikyyy.de/tempest/

That was a cool hack!!

I'm getting this as well, on an older dell 2407wfp.

Zooming in (i.e. making the width greater) results in a lower-pitched sound.

Zooming out (i.e. making the width narrower) results in a higher-pitched sound.

Great catch/explanation of this anomaly.

reminds me of how top gear was able to do similar with an F1 Engine https://www.youtube.com/watch?v=5BaR1Kc62Pk

It doesn't happen to mine but I can see how it could - the liquid crystal is driven with a high-frequency signal whose voltage basically corresponds to the intensity of the pixel, and when images containing repetitive content are displayed, that signal will follow the content of the image; the current that drives the display also follows that signal, and if the signal contains frequencies that happen to excite resonances in the audible range in some components of the hardware, you can hear it.




It's because of these horizontal bars, you can get the same effect with similar graphics:

All video interfaces we use transmit data serially, line by line, pixel by pixel. The bars are 16px tall (black + white) so at 60Hz and 1920×1080px they'll produce a tone with fundamental frequency of 4.05kHz (60Hz × 1080 lines / 16 lines) and harmonics.

This is way more fascinating than the site itself...

I'll confirm a tone shift on an HP ZR2740w as well. It's quiet, and I have to put my ear to the back of the monitor to notice as I alt-tab the window. But it's certainly there.

(I'm trying to get a recording, but I work in a plant and it's a bit full of white-ish noise...)

May be your age. Higher pitched frequencies are often heard by you youngsters but not us old folk.

Can confirm same high pitched sound on 27 iMac.

Plus: open developer toolbars, find styles for .bars, change margin-bottom and sound changes frequency.

Damn you for making me look like a fool with my ear up against the screen.

(No sound here)

Same here on my Monoprice 27" IPS LED monitor: http://www.monoprice.com/Product?p_id=10489

Does this work for for anybody on MBP or Retina displays? I tried mouse-wheel, trackpad and scroll bar, can't hear anything. anybody?

Nothing for me either with a rMBP

Same on my work LCD. Dell E207WFP.

I also tried test patterns at http://www.lagom.nl/lcd-test/ and http://www.testufo.com/. None of those made caused my screen to make an audible sound.

Same sound here - only on my external monitor though, not on my MBP's own screen.

I recently tested my new TFT (TN-panel) monitor with a monitor test application, and noticed an high pitched sound on a very specific blue line pattern too. I turned down the brightness from 100% to 80% and that reduced it.

My monitor also makes a high pitched noise. Sony KDL-32EX400 (using HDMI connection). Neither of my other monitors produce the noise (VGA, & Displayport connections if it matters)

Same here, I first thought it was the gfx card's capacitors. They usually like doing that when I use things with pixel shaders (obviously a different thing but it reminded me).

Furmark always does it to my cards. Perhaps of interest. http://www.hardwarecanucks.com/forum/hardware-canucks-review...

I have two identical monitors. One of them makes a high pitched sound on this page, and the other is perfectly fine.


Same here on a MBP.

Mine doesn't (Retina without ghosting).

Though, when scrolling on the site, _something_ (it's not the screen) is making weird noises, almost like the sound when accessing a HDD. I have an SSD though.

I had the same issues with other sites / applications when scrolling in general as well. Even more noticeable with the MacBook Air I had before. Is there any rational explanation for this?

The first thing to know is that the power consumption of modern CPUs varies hugely between idle and full-speed; from a few watts to several dozen.

When you are just looking at the screen, and the machine is otherwise idle, the CPU is not doing much, so it goes into low-power low-frequency mode and "sleeps" until some event occurs. When you put fingers on the trackpad and scroll, it sends an "interrupt" to the CPU, telling it that a scroll event has occurred; in a few microseconds the CPU goes from idle to full power to process that scroll event, then goes back to sleep again. The GPU might also be involved in the same way. Every little scroll movement results in an interrupt, so when you are scrolling at a constant rate interrupts occur at a fixed frequency, and the system is going from idle to full power many times a second. The pulses of power draw that this creates, happening at audible frequencies, causes various components like inductors and capacitors to emit sound.

I used to have a computer that did that a long while back. It made a whistle whenever I'd scroll. IIRC I decided it was the video card, though I'm not sure I ever confirmed it.

I've got a MacBook Pro, but slightly older, and I'm not hearing it. Mine still has the ghosting issue, which makes me wonder if that issue is stopping this issue.

Mine too. What is this sorcery?

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