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Why Does a Screen Re-Draw Make Noises?
grungy asks: "On several computers I have owned, I have noticed an audible noise related to large screen re-draws. A hardware guy once hypothesized that the large memory-move operation was creating electronic 'noise' which was then picked up and audibly amplified by my speaker. I unwired my speaker, removed it from the machine and put it in a different room, and the phenomenon still occurred. At this point I assumed it was something going on/emanating from the monitor itself. Now I have a TiBook laptop with an LCD panel. At quiet moments I can still hear it when I drag windows around. I have tried doing big memcpy's & the like, I don't get the same noise. I've been wondering about this for years. Anybody know what gives?"
Is it associated with a large change in brightness? Like in drawing a white box on top of a black area?
It could be static electricity, as it is suddenly going from one number of electrons to a very different number of electrons hitting the screen.
Gee, it's great to have an electrical engineer as a dad...
In my 3D grafix programming life, i never heard these noises :)
Consensus is good, but informed dictatorship is better
Whenever you have a flow of current, you will have a magnetic field generated, and that field reacts with the environment to cause motion. Even though computers are 'digital' doesn't mean that some how they are immune from the all the laws of electromagnetism we use to design analog devices like speakers - it's all the same thing. If nothing else, there is always the earth's magnetosphere to react with like a speaker's coil to it's magnet.
It's the same reason electrical transformers hum, and fluorescent lights buzz.
"I don't know that atheists should be considered citizens, nor should they be considered patriots." George HW Bush
I hear noises too... but my doctor solved that problem :-)
But seriously, could the monitor cable be near a power cable or speaker cable? I can hear interference whenever the two are nearby.
Can you hear the noise even if speakers are not connected or nearby?
Maybe this page (see the section "noise interference") may help: http://www.smmpa.org/atwork/pwrqual.html
Maybe it's all the little ``gates'' opening and closing inside the computer as the electrons flow through system. I have created this same noise effect by ping flooding a host in a test lab environment on a 100Mps Full-Duplex switched network---the network card was actually a four port and I may have been pinging all four interfaces from different systems.
LCDs do not have the electro-magnetic radiation that can be picked up by passing DOJ vehicles for license validations.
In late 1997, a secret comittee was formed and ushed in a new era of aural-based tempest radiation sensors. They created a bill that stipulated all LCD monitors needed audio broadcasting capabilities for governmental remote viewing. It was rushed through congress during secret underworld briefings and eventually passed at the Grand New World Order Council, codified in January, 1998.
Today these signals are still somewhat perceptible in the lower frequencies, but they emit a wide spectrum for large data broadcasts. Simple listening devices can pick up many user metrics, and are not limited to merely what's displayed on the screen.
I hope this answers your question.
This is consistent with the sound a monitor will make when tapped by the RIAA or the DEA (looking for bong dealers). You should immediately unplug the monitor, put it in the shower, and let the water run for approximately 15 minutes. Be sure to apply a good screen massage.
I used to be a MS fan but then I was brainwashed. Now I see the Light. Mac OS X pwns u.
I'm not saying you're crazy, but tinnitus or a related phenomenon could be part of the reason for the sound you hear. It's surprisingly easy to habituate yourself into hearing buzzing, humming, or other types of noise that can be interpreted that way. There are, of course, other possible reasons for why you hear the sounds (degaussing on a CRT, maybe). And there are certainly other physiological causes for tinnitus, too. But it's not impossible that you're causing yourself to hear sounds when you expect to hear them. There's an interesting article on habituation and treatment of tinnitus that might be related. The human brain is truly a marvel.
Just one consideration among others.
I have noticed an audible noise related to large screen re-draws.
Do the noises sound like sounds?
Do the sounds sound like words?
Are they talking?
Talking to you?
Telling you to do something?
Something like...
Kill! Kill! Kill?
Kill the nassssty hobbitses?
For the precious, preciousssss, preciousssssss
Ring?
Yessssss. Yesssssss. Kill the hobbitses!
Opinions on the Twiddler2 hand-held keyboard?
Perhaps it was the CRT on the first computer you mentioned and the speakers on the second. Since it was a laptop, it probably had speakers.
:)
My current computer makes such noise when using my Plextor burner - unless I switch it off in the mixer.
And my old computer made such noise with almost every operation, disc usage, mouse usage, hard drive and so on. Simply because it had speakers attached to the front of the case (a so-called Multimedia PC). The output of the sound card had to be plugged into the back of the case. I guess it was the radiation inside the case that influenced the signal on the way from the back of the case to the speakers at the front. It was really loud, but I could easily tell when something was wrong with my computer - then the sound changed
have you tried turning /up/ the volume of the speakers? /internal/ speaker?
yes, I know "The speakers unplugged blah blah blah", I'm not saying that it doesnt exist when there are no speakers, but the speakers could indeed pick up the noise.
When I heard this noise, however, I looked up on google, it said to turn your soundcard volume down from 100%, and boom it goes away.
Now let me ask you this: have you unplugged your
-- 'The' Lord and Master Bitman On High, Master Of All
I used to have a weird faint sound just on the edge of hearing show up, not when I was moving windows around but when I was sending packets over the network.
Whenever there was a lot of network activity, If everything was quiet, I could hear a faint sound.
I assumed it was just a cap vibrating in my cheap ethernet card, and swapped it out for a better one (when I finally switched away from 10b2).
The sound went away after that.
My tibook (800DVI) also makes a very low subtle static-raspy-buzz sound when I drag larger windows around. I think it's coming from the speakers. The noise happens even if sound is muted. I've noticed it for some time.
or at least get them from the grocery store instead of collecting them out in the forest.
That should solve the problem quick.
many systems use series of coils and other devices to format the voltages and frequencys with in certian ranges. I have noticed that duing some screen redraws I would get audable sounds on a PS-390 Evans & Sutherland graphics display while displaying vector graphics and no weird sounds in text mode. The system used a CRT, and other odd interfaces, but there was no speaker as such, and it would create audable emissions, and they could be viewed on a osciloscope with a microphone attached as input... I would reccomend that you approach this as scientificaly as possible by actually measuring the sounds, recording the sounds nad doing frequency analysis on the sounds. Then you could better asssertain what the problem is. On my current quick silver G4 there was a speaker hiss problem where you could hear audable noises out of the internal speaker during some operations with menus and graphics. The only solution was the attachment of Apple Pro Speakers to the G4 audio out port, though if you hold the speaker up to your ear you can still hear the noises, so it still has some cross over with the sound system.
The hissy-screechy-screech-screech that you're hearing might also be coming from the power supply. To the extent that it would carry into your audio circuit, electrical noise would easily translated to acoustic noise through your speaker/headset.
However, it's also possible that you have a marginal power supply that operates at switching frequencies that approaches human-audible frequencies; or the actual current draw changes from high-speed memory transfers within the graphic sections (board) has a human-audible frequency component to it that actually emanates from (say) the torroids in the supply.
People with very sensitive high-frequency hearing can sometimes tell the brightness of a television screen just by listening...
This could also happen from other activity -- I once had a 386 PC which, when running DOS, would emanate the tell-tale sound when it was waiting for keyboard input. It was kinda neat, actually -- I could go read other things while waiting for a program to finish its calculation -- and I didn't have to keep looking up at the screen...
I have this happen too!
I never noticed it on a PC before (mainly because they are so noisy, hdd's spinning, several fans inside spinning, air blowing, etc).
But on my Powerbook G4, i have DEFINITELY noticed this happening.
When its unusually quiet (usually late at night) when not a sound can be heard, and the powerbooks fan and hdd is off, i can very clearly hear this sound when i move windows around!
Its totally bizzare.... and its like a clicking sound that another poster described.
Its an extremely quiet sound, however, and usually you would never hear it unless its unusually quiet and your ears have had time to adjust to the minutest sounds.
If you have a tibook, try it.
I dunno if its possible with a normal PC, though, since they are just so noisy.
D.
You can tell how powerful someone is by the magnitude of the crime they can commit and be able to get away with.
This happened to me once. Try to determine if the noise comes from the LCD or from the computer itself. In the latter case, you should probably replace your main adapter as it's likely to give up soon. Normally happens when it's deteriorating or not strong enough in the first place.
Most notably on a Sun UltraSparc from which you could hear a hiss coming from the case (not the monitor) when scrolling a large body of text through an xterm. There were no speakers on the machine. I could cat a large file and hear the memory chips hiss. I think it was the memory chips from the location on the front right side of the case.
This was very repeatable, and could be demonstrated to anyone. I've had similar noises from other machines, but the fan usually drowns it out to where most people can't hear it and you aren't sure.
OK I have only noticed this on my latest computer.
..
its not only on redraw even just moving the mouse somtimes
but moving windows makes it louder.
it comes from the speekers and goes away if I turn them off but still its crazy....
p.s. My girlfriends, roomates computer talks all the time, no lie, she has a tv card hooked up to cable and ALL the time you hear a low wisper of the the TV comming through even if arn't watching TV at that time....
its fucked up....
--meh--
I've heard this on every computer I've owned, going back 14 years to my Apple IIgs. Any CPU operation (tight loops reading memory especially) could be heard as pitched tones on the audio out, especially noticable when listening with headphones. On the IIgs, I had a stereo "Audio Animator" card and always figured it was crappy RF shielding. You could hear a scale, tones changing as you moused over each item in a menu.
;)
But it happens on my other computers too, to larger or smaller degrees. On my TiBook, it's pretty noticable when the fan/drive are spun down. I program in Cocoa/GL and you can hear the tone change just by creating an NSTimer with different frequencies, and using it to do graphical operations. Most of the time, this results in a low 60Hz "hum."
I think it's due to RF interference between the audio portion of the board and whatever else is nearby. It seems more prevalent on laptops where everything is packed closely together but it's not limited to laptops, or LCDs.
Somebody should write an app that plays one-channel melodies with the RF noise...
When your CPU comes on and off of the HLT (halt) instruction, it creates a tiny electromagnetic field that is perceptible by your sound card.
you don't hear it on file copies because the CPU is steadily on, and not halting.
This is much more perceptible on Linux than on Windows (with the same exact computer) because linux likes the HLT instruction a lot more than windows does.
This is what I think it is, anyway.
I'm not sure exactly what you mean by moving the speaker to a different room... did you reconnect it? (unplugging it is sufficient, moving it is pointless).
I have heard monitors before... old Hitachi made Suns (as used on IPCs and SPARCstation 1s) with bad flybacks (painful if you have a high range of hearing). The tone changed slightly with the brightness of the screen, but was always there.
I am typing this on a computer that makes noise whenever I move the mouse or type, or during screen drawing functions. These sounds are definately coming from the speakers. If this is what you are experiencing, then your friend was exactly right. You will be more likely to hear it with cheaper sound cards/chips... and different video chips. The one I have is a horrible on-board sound-chip as used on a Tyan Thunder 2 (dual P-II board w/on-board sound & SCSI), the OPL3-SAX. It may also be the design of the board rather than the chip. Part of the problem is the video card, I'm using a Banshee in this box. When I toss in a sound card (instead of using the onboard chip), the annoying noise is greatly deminished, but still there (if you listen closely).
- Preferences: Solaris 10 (servers), Ubuntu (desktops), Solaris 11 (personal servers) -
*Turns Calendar Page*
Looks like it's Duplicated backplane dereferencing signal.
You see, the operating system has to keep a buffer of the screen in memory, and similar to dereferencing a pointer, the dereferencing of this backplane, or buffer, temporarily distorts the signal on monitors that haven't been serviced lately.
{DUMMY MODE ON}
Luckily, this is something you can quiet fairly easily. Do you have a screwdriver?
No, really, I have. Especially if I set the CD audio volume up.
/usr/lib or loaded up a web page, and they could hear the transfers on the bus. Its not a "normal" sound, more of a really dampened sound of like when computers used audio tapes to store programs and you played the tape in a audio tape player.
See I have headphones, if and you use headphones you can really here ANY activity on the bus, and thats not me being insane. Like any time and major "traffic" on the PCI bus takes place and I have the CD audio volume up, I can hear it. I guess the IDE controller doesn't isolate itself from the bus well enough.
I really don't know a lot about the PCI bus, but doesn't it have a high-impedience state (tri-state bus) for any device that is not active (hey just learned that in my digial-logic class)? Maybe it doesn't, I dont know. If it doesn't is that because it would cause a larger current drain due to the high impedicance? Not sure, really exhausted atm so I'm probably not making a lot of sense but oh well sorry.
Anyway, some of my friends thought I was nuts because I would say I could "hear my computer". But I let them try on the headphones and then I did a 'ls -alf' on
Apple has long acknowledged this issue. It has been in every laptop they have made. The problem is a capacitor in the voltage down-converter.
Previously the down-converter was in the top of the clamshell, but now it has been moved to the bottom case near the motherboard.
You can hear the same hiss/hum from the ballast in a florescent light. Since the backlight on a LCD is really just a thin florescent light.
If the issue is exceptionally bad, and easily reproducible you can send the machine into the depot for repair, worst case scenario you will not have your machine for up to 7 days.
You are hearing noises from yout computer?
Ok, this is what you need to do:
Listen to music. LOUD music. For years on end. Eventually, you will get to the point where you will no longer hear the noises coming from your computer. Problem solved!
Ehh? What did you say? Speak up, son!
I haven't lost my mind!
It is backed up on disk...somewhere...
It's the bus'es. When large amount of data passes the bus (e.g. the PCI bus), the sound-card might pick up these, since the sound card constantly listens for new sound-input.
I think I am having a similar problem, but on a different level. My server, which I newly built for $80, has an odd problem with the fan speed. I believe it may be caused by signal interference or something along those lines. Any extra interference will cause the fan speed to move up, for some strange reason. This usually occurs when the computer is doing any processing, like storing a file or dealing webpages. It is really odd, but I only hear it if I am trying to listen for it. So just stop listening and the voices will go away. (That is, unless you have a whole new kind of mental illness, where the voices control you, instead of you just taking suggestions) Something similar may be happening with the monitor, but I am not sure.
If all else fails, check yourself in to the local, conveniently located loony bin. Hey, it worked for me!
- - - - - - -
Orppf urp mf y.ppcxn. yflcbi otcnnov C am yflcbi yr n.apb Ekrpatv (Dvorak -> Qwerty)
thanks to microsoft's continuing innovation, the OS can make sounds whenever certain events (like opening windows) happen... all you have to do is turn down the volume ;)
They are all wrong...
It's a little guy in the computer with chalk, drawing the pictures on the screen. Sometimes when the screen "freezes" - it's him taking a break.
After a long spell at the coomputer you can usually hear him gasping for breath.
When he has run out of colours and he only has blue left - that when you get the BSOD.
For problems, seek only the simplest solution, complexity brings with it more problems.
Before, with CRTs and cheap LCDs, anytime that I moved a big window (typically bright, say all white), and wiggled it around the desktop, I heard something similar to a, "wheeeee, weeeeee" kind of sound (the 'wheee' matching the window movement). Of course, this was a very very high pitch sound; a quieter and higher pitched version of the whine that TVs and crappy old CRTs make. Now I have a new and really nice LCD... I can't really hear anything, but then again, maybe I'm just getting old.
;)
Isn't it great to know you have good hearing though?
This is a little OT but... back when I was a kid, I think I had even better hearing... I used to stay at my grandparents' house, and I could sense people walking down the hall to my room, no matter how quiet they were. The floor didn't squeak, and my grandmother used to walk around softly. But I could tell when she was coming. Basically, I would hear what seemed to me a lack of noise approaching; there was a lot of ambient noise from the living room (the windows were open which means lots of trees, birds, wind, etc. to hear), so someone walking down the hallway towards my room from the living room seemingly blocked some of the sound. It was very slight, but it was enough so I would usually be looking up at my grandma when she turned the corner to my room. I've had other experiences, like hearing if someone was sticking their hand in front of my face when I was blindfolded (it had to be in a fairly quiet room however).
Sigh, I miss having my good hearing. 25 years and lots of concerts, New years festivals and 4th of Julys will do that. It would be so helpful now to have that hearing, especially when my boss walks to my cubicle
0- Eamonman Proud member of DNRC
Generally computer screens emit AM radio waves whenever they work, it is possible that when you do a large screen re-draw it eminates a specific wave length that affects your speaker...
Personally this has never happened to me but it's possible.
BTW it is possible to capture your screen using an AM reciever, also the reverse is possible as well - you can use your screen to broadcast music (by emulating the music into a screen image that will broadcast the music) I even saw a program that does this for MP3, but I forgot the name...
...When you're 40, you won't hear it anymore. Young ears hear much higher-pitched noises than old fogie ears.
Since the PC has a TFT screen and an external power supply, I doubt that these have anything to do with it...
The fact that computers generate RF noise was put to great use by a program for the Sinclair ZX81 (which had no sound hardware). The program caused oscillations which, if you turned the TV's sound up, were audible as tones.
I have a Compaq Evo I use at work. If I am listening to my headphones, the cheap ones or the hundred dollar ones, I get a static noise that changes pitch and cycle rate when I type, move my mouse, click on things, open files... It is really interesting. It is almost like the computer is telling me what it is doing. Of course this becomes irritating after a while, because I have heard enough from it now.
Just a friendly suggestion.
You asked slashdot so I could ask google for you instead.
When capacitors are charged and drained quickly, they can emit sound. As the charge changes, the two plates that hold the charge will try and move closer or further apart, in a similar way to a speaker. Unlike SRAM, DRAM is actually made from banks of tiny capacitors. In older machines, you could often hear the memory singing while the bootup memory check was in progress.
While you can't hear a bit changing here and there, when changing large amounts of memory very quickly, such as changing/redrawing a screen, the sound soon mounts up, and you can hear it.
--[me]
I've had a similar issue with a few systems, in my experience its been the sound cards at fault. My main workstation had an embedded audio card, (I figured I didn't need that good sound), however when I moved my *mouse*, I could hear it out the speakers when they were turned up. When I connected the output of the MB to my stereo, it got even worse. I disabled the internal audio card, and replaced it with a cheap PCI one, and it fixed most of the issues.
I'd suspect the same sort of issue with laptops, since they usually have embedded speakers, you may find the same interference.
You mention when all speakers are removed from the room, you can still hear the noise. I would suggest using a stethoscope to locate the source of the noise. (Your ear may work, but ears are notoriously bad at locating certain types of sounds, the same type I suspect you are hearing). It is almost definatly comming from the monitor, at which point I'd assume its due to the HV circuitry. If this is the case, try changing the video refresh rates, and see if there is any other change. Also note what changes creating the noise. Eg if you create a white box on a black background, does the noise appear, maybe only when moving the white box?, etc.
Treat this like a physics experiement, assume nothing, and test, then retest basic hypothys: "Ok it happens when I move this window, so now if I reduce what I'm doing to the simplest test, eg a black box on a white screen, does it still happen?".
If, in the unlikey event, its not comming from your monitor, check your PC speaker, it may be picking up the noise... maybe.
I use to have a funny sig, but slash cut it off, and I forgot what the punchline was.
When you do stuff, the CPU draws more current. This could affect all the chokes and stuff in the power supply. Small chopper PSUs such as those used to regulate down the 5v/3.3v rail to the 1.5~odd volts that modern CPUs need have several inductors, which could vibrate and make noises. Especially when attached to a big wobbly fibreglass sounding board.
Properly designed hardware should not do this.
A few weeks ago, I thought my Soyo Dragon motherboard had gone flaky because I was getting massive fs corruption when copying between drives. I panicked and went out and bought a new motherboard without having done any research. I told the guy I wanted to replace a Soyo Dragon and had 5 IDE devices, including 3 7200 RPM drives. The moron gave me an MSI KT3 Ultra2. That is not a replacement for a Dragon. The onboard sound doesn't even have digital audio outputs. I was using the Dragon's SPDIF to connect to my speakers. It sounds very nice.
I tried it out anyway. One thing I noticed right away was that I could hear noise whenever I selected text or moved a window. I took it back (for other reasons as well) and got my money back. The fs corruption was caused by the power supply unable to put out the power so I got a new one.
Right now I'm using the Dragon's analog out and there's no noise at all at any normal volume. If I turn everything up to maximum, I can barely hear something above the fan noise, but if I play something at that level, my ears would hurt.
Plugging in your monitor to your PC turns it's cable into a giant antennae. Just like TEMPEST. When a bunch of changes are made on screen the signal going to the monitor fluxuates dramatically. This fluctuaion is picked up by the antennae that is your speaker leads.
RF shielding and those magnetic cylinders on the cable help to reduce this.
However you still have an energized cable with radiply changing frequencies flowing across it. And those frequencies radiate and are picked up by other antennae and transmitted along their length.
Have fun sometime and put your cellphone next to a boombox with the volumed cranked up on a dead source. Then call the phone and listen to the funkiness.
One good thing about music... when it hits you, you feel no pain. So hit me with music. -Bob Marley
I have the same problem with my LCD iMac. It's not attributable to simple CPU usage, but rather the interface. When I drag windows, move scroll bars, access menus, etc., I hear a slight grinding sound (sort of like a hard drive but considerably quieter).
Then again, when I've got iTunes blaring it doesn't really matter.
Gabriel Ricard
:-) yet another reason to be running distributed.net
or some other ways to tie up your cpu. After all, if you are not using your processor, those cycles are just going to waste.
Did you mount a military-grade, variable-focus MASER on an unlicensed artificial intelligence?
On that laptop there's a power inverter board right near the back of the unit, near the built-in speakers. If that unit is not performing correctly then the power change needed to actually change the million pixels on the LCD will cause a fluctuation in the EMF it emits. Being so close to the BUILT-IN speakers, you'll likely hear the buzz there even if the sound is turned off as the EMF itself is driving the speakers.
Does the sound change when the brightness is turned down? If the above is right, then the sound will not be as loud when the brightness is turned to one notch above off.
I have a Belkin WiFi gateway through which my half a dozen machines talk. If I control a remote machine using VNC a screen redraw causes the gateway to make quite a pronounced rustling sound as if you can hear the packets going through it.
My vote is for the RF noise being picked up by the unshielded soundcard. Just think --- the companies making the cards are constantly trying to find ways to make them cheaper. I mean, just how far can they go adding new features before the average person can't tell the difference anymore. The only thing left at that point is to find ways to make your product more cheaply than any of your competitors, and one way to do that is to not bother with the engineering involved in making an RF shielded card... "Hate my people? I love my people! PULL!"
turning off your microphone? Worked like a charm for me.
I also reply below your current threshold.
As for what causes this, I am at a loss. But I have noticed that it is very pronounced in my cheap $8 headphones, while unnoticeable in a pair of higher quality. I also cannot hear it when using decent speakers, though I can when using cheap ones. But using the cheap headphones or speakers with a walkman-type device or stereo does not induce the noise, only when connected to my computer.
An interesting test would be... Take the offending speakers or headphones and connect them to your walkman/cd player/ipod/whatever and sit at your computer. Do you hear the noise? If not, and if it only occurs when the speakers/headphones are connected to the computer, then the noise may be internal to the system, the problem occuring at the soundcard, and better speakers/headphones filter it out.
How are you going to keep them down on the farm once they've seen Karl Hungus?
I've noticed since I was young that television screens also make noises. Particularly when going from black to suddenly bright.
I have a gateway ev700 monitor, and it does it. This is also the first monitor of mine to ever do it.
When I minimize this window, the first time it makes a noise like a poof, that is just like a small, quiet version of turning a TV off going into power save mode. The window has to be up a while - it only does it once in a while, and never happens in fast repeated minimize-restore successions.
Incedetally, the monitor is mostly white (/.'s color scheme) and gets filled with win98's default green when I minimize. I think the difference in colors is key...
Slashdot's rate-of-post filter: Preventing you from posting too many great ideas at once.
I'm amazed at the number of answers from the "Slashdot experts" and yet I don't see the correct one yet.
The noise you hear is actually fairly simple to explain. First of all, people should realize that this is not RF noise coming through the speaker, as you tried to explain. This is a noise generated by the vibration of a system component.
Your graphics card is the culprit. Remember that your hardware is full of clocks(vibrating crystals) and switches(transistors). These microscopic components move or vibrate at very high frequencies. Vibration creates noise, as we all know. But, the vibrations(or frequencies) change when the image on the screen changes. Certain colors and certain movements on the screen create frequecies that are perceptible to human hearing and you hear a slight buzz or high pitched whine form your video card.
If you want to test my answer, try changing the frequencies for your display and you will hear the sound come and go. You will also notice the pitch will change when different frequency setting are used.
Some hardware is less prone to this because of thicker cladding or more secure mountings but, they all do it. It's just that some equipment is louder than others.
usually in dc-dc converters there are transformers. and those windings will hum when a load is put thru them.
for an lcd (at least) you need a big step-up voltage to drive the backlight. on my dell laptop I hear noise near the keyboard area and I think its due to a dc-dc converter showing some signs of age (it didn't make much noise when it was brand new).
--
"It is now safe to switch off your computer."
...bury you TiBook in the forest and leave it there....does it still make screen redraw noises? ;-)
If one more person mentions the sound card I'm going to scream. READ THE POST! He disconnected his speaker, gone, killed it, no speakers at all!
:P
Now that we know it is physically impossible for the SOUND CARD to generate the sound then we can look in other areas.
I have also noticed this event in all my PC's. I have always attributed it to the fact that the monitor is changing how the guns work, however as it seems to also happen with LCDs I'd have to agree with the capacitor posts.
Do you get the same sound with the monitor turned off? If not then it is the monitor. If it is still there then its most likely a result of the capacitors. Could there be 2 distinct noises? 1 from the monitor and 1 from the capacitors?
Another thought, try using a smaller font.
I know when I turn off the external speakers on my stereo and unplug my headphones from it, turn up the volume all the way on my stereo system; I can hear the music coming from the amplifier without any speakers, maybe this is related?
Natural-Selection Be
However, on RH 8.0, using X windows or without, the screen emits a fairly loud buzz that only goes away when something on the screen is moving.
I don't know if I have especially good ears. I suspect I don't, but this buzz is maddening.
So the point is, you might be able to attribute some of the noise your monitor makes to the driver, the refresh rate (though changing it hasn't worked for me) or some factor of the driver.
There are no trolls. There are no trees out here.
Just be thankful its not as loud as on TV or in movies. The screen beeps or makes some kind of noise for everything.
At least in my case. The ixMicro TwinTurbo128 that was in my Umax S-900 would hiss white noise (well, more towards gray, actually) when dragging large windows, but there were also other more subtle things. I hadn't actually realized that I no longer heard it till I saw this 'story.' I gave that computer to a friend who happens to run a home recording studio so I'll have to ask him if he's experiencing that.
I'd also noticed sometimes that having a menu held down would do something similar, but I think only when running Mac OS 9. OS X is a totally different beast, acoustically speaking. Any Mac user can tell you that a fast SCSI hard drive sounds *noticeably* different when booting the two (I have a sounds-like-jiffy-pop-under-a-pillow model, but when booting X it sounds more like a stun gun with a subwoofer), so maybe the video noise is really a feature of some twisted sort?
On a mostly unrelated note, I leave my cell phone sitting under the front of my CRT so I can see the image shake when it phones home once an hour, and answer it before it rings. (Hmm, either Slashdot is suddenly epileptic, or my phone's about to ring...)
Quantum materiae materietur marmota monax si marmota monax materiam possit materiari?
Some crt and televisoins will produce a large amount of high frequency audable noise from the horizontal synchronization circuit when displaying certain amounts of light.
An all white screen can do this
Ever walk down a street on a quiet evening, and you suddenly hear the deep thrum of 60 cycle hum? The noises you're hearing may be eminating directly from the coils inside your CRT. This sounds cool but actually I doubt thats what it is.
I know the sounds you're talking about. I've noticed them to a greater or lesser degree on lots of different computers, beginning with my Apple IIgs. Not having a fan, it was totally silent when there was no disc access. You could always hear faint little noises when it was doing stuff.
The problem is simply corrolated noise. All the little bitznbytez on your motherboard throw off lots of electromagnetic energy when they're doing their thing. The sound card/pc speaker amplifier, being imperfect, picks up and amplifies some components of that noise. The sound card/pc speaker also picks some up directly from the PCI bus, and also generates some of it's own. I'm going to bet dollars to donuts that while you may have taken away your multimedia speakers, you forgot about your PC speaker...
-73, de n1ywb
www.n1ywb.com
Actually, I've been surprised that no one has noted that the detectible frequescies are almost certainly not the computers electrical signals or RFI *per se* but the resonances and beat frequencies of high frequency signals and/or general pseudoregularities in signals and pulses generated in various parts of the computer.
Most people are familiar with one definition of resonance - that even tiny signals can sum over time in a resonant cavity, physical object, circuit, etc, and build to remarkable amplitudes in a few hundred or thousands cycles.
Most people are also aware of harmonics. A square wave of amplitude 1 and frequency w can be defined as the sum of sine waves of amplitude 1/k and frequency k*w (where k is any odd integer) Of course, k*w is a *higher* frequency component,and soon gets too high to be transmitted in the system without attenuation, which leads to the inevitable rounding of the shoulders and imperfect on/off transitions of real-life digital square waves.
High frequencies can reinforce (pump) mechanical and electrical resonances that are any integral fraction w/n (where n is a positive integer) of the original signal, and to a lesser degree, any integral ratio of the signal frequency w (w * p/q , where p and q are integers) In both these cases, we get *lower* frequency effects (e.g. mechanical vibrations in physical objects like brackets, casise panels, etc.) which are more likely to be in the range of human perception.
Beat frequencies result whenever two different frequencies are mixed. (w1 -w2) so two very similar frequencies can easily create a frequency in the audio range.
There are a cacophony of signals inside a computer: system clocks, regularities in the pulse trains of certain signals (e.g. long term bit pattern repetition, to fill a window with a color) the various analog control signals inside a hard drive, sound card, tuner card, etc. -- plus all their multiples and fractions, plus all the mechanical resonances of every component and assembly inside the case.
It's not surprising that SOME of these signals or components will be sufficiently mutually self-reinforcing in an audible range, varying between computers and with various actions/tasks.
The mechanical resonances of physicial parts or assemblies in particular, are likely to fall in the audible range, and are likely to generate physical vibrations that that will be tramistted through the air as sound. This is a familiar effect to any discerning audiophile who has tried building their own speakers and enclosures.
I had this problem with my machine (athlon) and changing the power supply fixed it. I went to a higher quality PSU, with higher power output.
I did notice this problem with a laptop I once owned that always occurred when it was in Windows, but never in Linux too, so I guess there are multiple causes for this problem. I never figured out the reason for it on my laptop.
Not off topic, moderators.
OSX does not have the interface sounds available anymore, and even if they were, those were not the sounds I heard. However, there is a haxie from Unsanity call Xounds that adds this capability to OSX.
Gabriel Ricard
there is a related thread here
here
You need to get a 10K rpm 80+ CFM Black Delta fan on your CPU, man. Guaranteed to take care of all noise, including the road construction in front of your house!
Code poet, espresso fiend, starter upper.
Transistors do not vibrate, and the clocks in your system are running outside of human hearing range, which is 20 Hz to 20 KHz. Unless you have some component clocked within that range, it'd be impossible to hear. Considering that 1 MHz is well outside human hearing range, I doubt that anything on your video card would change -- especially in relationship to colors and shapes which are simply a function of turning on and off different transistors all running at the same clock speed.
This is all utter and complete bullshit. YHBT. YHL. HAND.
Author wrote weird noises can be heard while dragging a window... I've met few mices that made lot of electromagnetic noise when moved. Also my Toshiba DVD drive makes image on my screen to shake a bit while grabbin' audio discs...
I especially notice this with the DirectDraw test that displays a series of concentric white rectangles on the screen, with my old monitor. There's an unmistakable whine. I can also hear when a TV switches to high brightness abruptly, if the volume is turned down enough and I'm close enough to it.
Omnes arx vestrum sunt adiuncta nobis.
Reminds me of Tempest for Eliza
Since you are probly using windows it is your harddrive since windows has to swap all the programs out of memory inorder to do large screen refreshes.
Late at night when it's very very quiet, my TiBook makes a barely audible noise that sounds like a quiet cat purr, which I must admit is somewhat endearing. As I move windows the purr becomes slightly more granular, but still not unpleasant. I've come to think of it as an added "feature."
A very low tech ear-to-speaker auditory location test has revealed that the noise is indeed coming from my speakers
...but I can ignore them most of the time.
I am very small, utmostly microscopic.
Since I haven't seen a cogent explanation posted yet, I'll take a swing.
Fact 1. 60 Hz transformer hum is unrelated to what you're hearing. (That would be at 120 Hz and relatively independent of screen refresh, which doesn't match your symptoms.) As a sidebar, 60 Hz hum is caused by the Lorentz force between the electric current in a transformer coil and the magnetic field that the current induces, which produces an radial outward force on the coil. (This effect is what limits the size of magnetic fields we can create in the laboratory -- no one wants an exploding electromagnet.) As the 60 Hz alternating current runs back and forth through the transformer, a 120 Hz mechanical vibration is induced.
Fact 2. It's also not directly related to "CRT whine". We can tell this because: (a) CRT whine is independent of whether screen contents are changing, and (b) CRT whine is a directly audible mechanical vibration, not a crosstalk into your audio out line. CRT whine is caused by the electronics that drive the electron gun's horizontal deflector. For example, if you scan 500 lines 60 times a second, the signal on the horizontal deflection plates is at 30 kHz, which some people can hear. Most modern computers have enough scan lines and a high enough refresh rate that the signal frequency is too high for anyone to hear, making this not a common problem with newer computers.
Fact 3. What you're hearing is caused by capacitive coupling between signal lines (wires) inside your computer. Because of the electric repulsion between electrons, high-frequency signals can "conduct" across the air between separate wires, especially if the wires are close together. In your case, it's crosstalk between the display and audio circuitry. This crosstalk interference can be reduced with grounded metal RF shielding, but it adds cost/bulk/weight and so manufacturers try to minimize the amount they use. An audio company would shield the DAC and preamp components carefully to bring the noise below a perceptible level; a typical computer manufacturer will just make it sound ok for ordinary use.
My guess... ...is that you have an active-matrix LCD screen, not a passive LCD or CRT. The reason is that you only hear the noise when the screen content changes. Unlike the other two, an active-matrix screen has transistors at each pixel that remember their state. Thus there is a drive signal to the screen only when pixels are changing. Only if relatively large portions of the LCD are being continually rewritten will the duty cycle of this drive signal be substantial, and therefore the crosstalk be audible.
Conclusion: It's annoying, but there's not much you can do about it without buying a higher-quality (i.e., better-shielded) audio card.
This is very simple: Bus noise + EMC problems. Bus noise is generated by the fact that the lines of a PCI slot change when another PCI device is accessed. This causes any bad Sound Chip to generate noise, and cannot be covered by shielding. The EMC is easier to deal with: cover your soundcard in aluminium.
Jos
Wow, you're remarkably ignorant for someone who can spell. ,3 ,4 , 5 etc, and at 1MHZ+/- 1KHz, etc with your 1MHz clock example.
"Transistors do not vibrate", eh? Fine. Short out your stereo amplifier's outputs and jam the volume to maximum power in a quiet room. You *WILL* hear the output module play the music. All those electrons in the die do make it a bit bigger (like charges repel, right? Remember high school physics?)
Oh yeah, I mean a real amplifier, like 100W per channel.
As for the rest, I guess you never worked with anything digital in your life, much less used a spectrum analyzer.
Look, chum, program loops repeat in a definite pattern that create the same access patterns on PCB traces. So if you have, let's say, an interrupt every millisecond that calls a routine to check the same things every time, and assuming nothing else happens, you will get harmonics at 1KHz, 2
I think you're an university student to be that ignorant. Usually it's electrical engineers who know the least about electronics.
PS: Why do they tighten industrial SCRs with thousands of PSI if they don't vibrate?
My Zaurus LCD screen also hums. Hold it upto your ear with the screen on and off, using
s p? siteId=1&jid=213AFD44133E1BAF474E5FE946E35618&cata log=0§ionId=0&productType=2&platformId=9&produ ctId=45601
http://www.handango.com/PlatformProductDetail.j
(free)
It's a whirring sound unlike CRT change in brightness.
A blog I run for the wealth
I'm not sure about LCD's, but this problem is well known with CRT's. Most monitor manufactures know about the issues, here's a sample:
q _t roubleshooting.html
http://www.maginnovision.com/Service_Support/fa
Basically the flyback transformer and deflection coils all may vibrate in the range of human hearing. Both can have the current (and thus, frequence) change as the image changes. Some people can't hear this at all, some can only hear when the change is happening, and not when the image is static.
In a laptop with speakers I'd much more suspect the graphics card, most of which are really bad about generating RF, is generating sounds that are being picked up by the speakers via induction.
On old TV's it's usually the flywire transformer. Often, you can "whack" it and break the resonance for a short period. As high frequency electricity travels through it, it "whines".
Electricity has lots of properties that can move objects. (Electric motors are an obvious example, speakers and piezo devices are others.) Electricity is pretty good for making sound. High voltage electricity is better. Computer displays and TV's tend to have both.
Electstatic speaker project
I think your TV scans at 15khz and uses big magnets and electric fields. Your old fashioned monitor does the same, but probably at various rates depending on the resolution you've selected.
I often hear the hum of the dispaly on my old Palm III when I turn on the backlight.
When large areas are being redrawn, that just adds another factor that changes what is going on. It might add a beat frequency that you can hear. It might disrupt a resonance that was hiding or exposing a constant state sound. On the other hand, while I play with high voltage regularly and sound occasionally, IANAAE (I am not an acoustics engineer.)
If you watch JAG or other TV shows... whenever text gets drawn, there is that sound.
So the computer people made it do that because Holywood did it, and established expected behavior.
Actually, somebody already pointed out electromagnetic stuff...
whenever there is a current of electricity, a magnetic field is generated.
A constant magnetic field provides a constant force, and then everything is in equilibrium.
Then when you move a bright window, the electromagnetic field moves. (the noise is comming from the monitor most likely)
and then that mask that seporates the pixles probably vibrates... making a sound.
(there are other things that can move too)
Please use [ informative / summarizing ] SUBJECT LINES
Flame me here
High output, can be heard by people with some decent hearing. Used in laptops, with the casing removed you can hear them quite well. Usually mounted next to/beside the LCD. Fuck the fucking fuckers!
Buy some new moderately priced ones.
My old Yamaha's died. Had to dig out my old Labtec speakers.
The Labtec speakers pick up.. radio stations. If everything else is quiet, I can hear, faint, but definite, various radio stations.
My Yamaha speakers, while around, never had this problem. Why? Probably something to do with proper insulation and all - IANAEE.
I have noticed an identical problem on my machine.
However, switching from onboard sound card to a PCI card (a Sound Blaster Ensoniq) gives me perfect silence.
Just my 1 1/2 cents.
I'm amazed at the number of answers from the "Slashdot experts" and yet I don't see the correct one yet.
Yet you also fail to give a correct answer too.
Even though some claim they (dogs probably can) hear their video card HSync signal, most of the time what you hear when the speakers are off is static electricity discharges like when you degauss your monitor.
On the other hand the sounds the original poster refers to are most probably caused by the induced voltages in the speakers from **changes** in the nearby electromagnetic fields emanating from the front and back of monitors (especially the cheap ones with crappy farady cages), as the screen content and colors change. Conditions that maximize this would be high contrast patterns, like alternating bands of bright and dark, since those cause more change in the electromagnetic field, which maximizes inductions in nearby conductors, like the coils fo your speakers.
Maybe it's synaesthesia?
I have some amplified speakers hooked up to my reciever in my living room. The speakers take XLR input, while the reviever outputs to regular speaker wire. After hacking up the XLR cables, I noticed that I got the same effect as you had. I could very audibly hear sound coming through the speakers when they were powered but had no input. I believe it was the God channel, but I'm not sure. For some reason, I can recieve the God channel on TV even when there's no antenna input plugged in, so either the transmitter is very close to me, or Jesus is trying to tell me someting.
Using unhacked XLR cable with a very short length of speaker wire fixed the problem. I was using a long length of speaker wire and a short length of XLR when I was having the problem. Shielding was the problem, it would seem.
On several computers I have noticed sounds (it's a clicking or thumping sound) that occur when the mouse is moved, proportional to how fast it is moving. Does the sound only occur when moving a large window, or does mousing while the window (or similar screen content, e.g. white background etc.) is visible?
Caveat Emptor is not a business model.
The first cassette recorder I had for use with a computer did not have the ability to mute the sound while loading. Some tapes needed the volume up particularly high to load properly. I recall being sat there, ears bleeding, in dismay at the "Data? Rewind tape" error messages appearing on the screen.
I think I remember a Sinclair Spectrum magazine running a type-in listing of a program to play music on a nearby radio. Could be mistaken, though. I remember a friend painstakingly typing in a program to record short sound samples through the cassette interface - possibly an Amstrad computer? If you used your imagination, and had prior knowledge of what was being recorded, the resulting crackle wasn't far off!
I've heard re-draw noises too, on an older monitor I had. Every time I so much as moved the mouse, there was an (almost high pitched) buzzing. If I didn't have some music playing, it would get irritating. (Although in general, that monitor was irritating.... it flickered too.)
Now I've switched to a new monitor, a Mitsubishi (can't remember what the other was, cheap and nasty as I recall) and I don't hear the noise anymore. I'd switched video card some months before, from a TNT2 to a GeForce2, and the noise remained.
I don't believe I had moved my speakers during that time... at least, not enough to have made a difference; the positioning was more or less the same.
I'm guessing it's a mix between monitor and speakers, and the cheap and nasty monitor had a greater (and more annoying) effect upon my speakers than my new monitor. I know I don't remember hearing that noise since I got the new monitor.
I get audible pops when my monitor switches resolutions (say 1024x768 to 800x600) or when I switch heads (it's dual head - er, in english, it switches between two computers to display on the same monitor). I have another monitor that makes no noise whatsoever. I believe this is similar or the same as the magnetic field thread (physical switching occuring)...
My knowledge of LCDs is very out of date, but I suspect if it supports multiple resolutions and doesn't display a shrunken image, there must be some kind of state change as well. All the portables I've ever used just used a portion of the screen if the resolution was higher than allowed (so 800x600 screen showing 640x480 would draw in the middle of the 800x600 screen but still be the same size).
I get noises from xfers to one of my IDE drive. muting the "line in" on my sound card stops them. I would think but choose not to :) ...
--Casey
my mitsubishi display sometimes starts making that noise and its *REALLY* annoying, ... like some of u guys explaining this in this page, my friends look at me like im crazy when i try to explain them.... of course, they dont hear anything.... : S
The thing that sometimes works with that is to change the colordepth from 32 to 24 or 16 bit, or the other that works always -at least with my computer- is to change the refresh rate from emm, "optimum" to 75hz or 68 or so.
Candy bar for the parent, his surmisal is 100% correct. Keep in mind that the author's primary mention was a TiBook. Move the windows around on a TiBook in Jaguar and you get cat-like growling noise. It's due to the graphics chip suddenly going into overtime work. This happened on earlier versions of the operating system as well, but not nearly to the degree that it does in Jaguar. Why? Because Jaguar makes heavy and unusual use of the graphics processor through Quartz Extreme. The sound does NOT come out of the speakers -- listen closely and you'll find that it comes from the motherboard itself.
Ummm, am I the only one that thinks this discussion should be moved to USENET? I don't think this type of topic should be in Ask Slashdot. This is more of a news reporting site with discussions about the news topic. I also understand what Ask Slashdot is used for, and it's great, but not for something this small and insignificant. It's great with a discussion about IT jobs or RAID when it is a major discussion that can solicit thousands of replys and strikes a nerve.
What's next, a discussion about why monitors attract cats? Or the ratio of game playing versus wife berating?
Don't flame me because I'm beautiful.
He gave EXACTLY the correct answer with respect to the original question. The poster had a G4 Powerbook. His answer *is* why the G4 Powerbook is making the noises it is.
You're one of those guys who can "hear" speaker cables. There was a saying among high-end audiophiles (redundanct?): "If you think you can hear speaker wires, then you shouldn't be left alone with small children." While I don't doubt that even things like high screen refresh rates are annoying to some, and flourescent lights to others, I've never, ever in my 22-23 years of computing heard of anyone "hearing" screen redraws. Come to think of it, my monitor (21" flat Trinitron) has started to make horrendous cracking sounds lately, in the middle of doing nothing!
there are quite a few people that can hear the extremely high-pitched whine of CRT's scanning - we can tell if a TV is on in a room without looking with it on mute
God, I'm glad to hear somebody else mention that. My girlfriend and I can both hear this, but nobody else in her family or mine can. Her entirely family turns off not the TV, but just the cable box, subjecting us to high-pitched whines from throughout her home at all hours of the day and night. Once, we were housesitting, and we heard the damned noise everywhere. Turned out to be some kind of ultrasonic mouse-trap dealie. It damned near made us insane.
-Waldo Jaquith
I get this kind of noise from my lcd panel.
I'm betting if you turn off the lcd panel and recreate the same actions you won't hear anything.
It's most likely componentry casing vibrating in response to the ebb and flow of electricity within it. This energy dissipates as heat causing minute expansions and contractions on the device casing in accordance with this ebb and flow. This can in turn, vibrate the air around it. On digital processing devices, the aggregate amount of energy inside the device is often a coefficient of what that device is doing. Some CPU intensive activities will result in energy waveforms that fall within the audible spectrum.
I used to work in a hardware lab designing laserprinter controllers when I was younger and had spookily good hearing (wrecked it using Pink Floyd). As a consequence, I could freak out the older engineers by "hearing" when a controller card was busy.
YMMV...
I was playing Splinter Cell on my comp, and when the screen would light up all white I heard a very obvious high pitched sound coming from my speakers. It was annoying to say the least. I've read through a ton of hypothesis, but I really haven't heard from anybody about a solution. One suggestion was for those lead rings around the cables to limit how much interference they bleed. Are there audio devices for removing electrical noise before it reaches the amp? Or will the sound get to speakers no matter what? (My speakers stopped making the sound when they were unplugged from the computer, so I'm sure it requires a direct connection for the noise to be carried). Also, the screen I'm typing on is almost all white and I don't get that noise, yet a heavy 3D oriented game like Splinter Cell makes my system shreak like a banshee.
-- I have an extremely witty sig, but you're not good enough to see it.
I actually had to make several trips to the audiologist over this same issue, it turns out that about 60-70% of the population has hearing in the well known range of 30hz-20khz and that the rest of the popuation has various hearing ranges dictated by physical problems and/or genetics.
About 5% percent of the population has hearing far above average, mine was tested out to 10hz-42khz. So, yes, I hear TV's / Plasma screens / LCD's / Flourescent Lights and when I lived in the L.A./San Diego area I could even hear earthquakes coming about a minute before they actually would start shaking the apartment building. ( Hence the trips to the audiologist. They actually sounds kinda like a Freight Train, if you have ever stood next to the track while it goes by. Except the Doppler Effect seems greatly exaggerated - maybe the effect of the wave traveling through the ground?)
When talking to an EE friend of mine, he recalled from his TV Repair days the Capacitors would switch states around 30 thousand times / second in accordance with the power draw of the tube for the color changes that each pass of the electron gun has to make and that the larger the tube the higher the frequency. ( So if you pay attention you will actually hear the sound change with the color being displayed on-screen)
Which makes sense, because my 13" RCA caused me no end of pain, so I stopped using it, When I went to buy a new set I actually convinced the sales people to turn off the other TV's in the show room so I could go around and find the TV that was the least offensive.
It's possible that the video driver is busy polling the graphics waiting for the drawing operation to complete. Check your CPU usage - does it go up when you drag a window around?
Chances are that when the CPU is idle it goes into a 'sleep' mode and draws less current. When it's polling the gfx card it obviously takes more current.
The sound is probably coming from the CPU's PSU inductors and is of the same audible frequency as your mouse refresh rate. I know of quite a few SMPS's that make an audible 'tick' whan current consumption increases.
I could hear my old 21" TV set, but when I replaced it with a new widescreen HDTV tube set, I noticed that (AFAIC) it's dead quiet. Probably due to that higher scan rate with all the extra lines.
does he wipe with the rabbit?
Truth isn't Truth - Guliani
I was checking something on my Palm m500 late at night once (when my surroundings are generally very silent), and had the backlight on. I noticed a high-pitched hum, and held it up to my ear. Sure enough, it was makin noise. I turned the back light off, and the noise was still present, though I think it was less amplified.
Check your handheld, is it singin?
-kidlinux.
if you're using integrated audio (AC97 or PCI based) they may have routed the outputs for the codec past the PCI or AGP data lines... there's so much high frequency traffic in those lines that it can't help but get picked up...
:)
The worse offender is typically the mic... because you often have at least 10dB of gain (even if "mic boost" is turned off)... so it ends up picking up system noise.
it's a kin to hearing cross-talk from line2 when you're talking on line1 on the phone... since both wires are run so close together (in this case in the same jacket) they end up picking up some noise from the other.
Video is notorious to audible spikes... a typical PNY PCI video card will cause huge (-40dB) spikes in the 7, 14 and 21kHz range... while traffic from a PCI NIC might only raise the general noise floor to -60~70dB, without causing spikes.
How do I know? I just had to diagnose system noise on a new design for an OEM
When I had an ISA sound card back in my 486 days, I could hear all kinds of things going on, especially window paints and the like. When I flipped to a PCI soundcard the noise subsided into the barely-audible-when-the-amp-is-on-full-blast range. So my bet is that you are hearing noise being picked up from the bus. Of course, as more and more items in the system get their own separate bus, this problem should become less and less noticable.
To test, memcpy etc. will not generate noise on the PCI bus so you have to do I/O there. Network traffic, SCSI activity on an installed PCI card, or loading and unloading data from the soundcard without actually playing anything should demonstrate the effect nicely.
One other thing related to bus / card noise. I recently pulled out my SCSI card and found that my TV tuner's image cleaned itself up immensely! And I had been thinking that I just got a crappy one for all these years...
Impression Monitors
to summarize two relevant points
[taken from the text of the troubleshooting guide]
2) I hear a low buzz coming from my monitor. Is something wrong?
No.
What you hear is the vibration of the vertical deflection coils sweeping the beam during the vertical refresh of the display. Since it operates from 60 to 76 Hertz (cycles per second), depending on the refresh rate your controller is programmed for, it is within the range of human hearing. You cannot detect the resonation of the horizontal coils because the frequency is from 30,000 to 64,000 Hertz which is so high it is inaudible.
3) Sometimes my monitor makes a high pitched noise. Is this a sign of trouble?
Usually the sound is from one of the transformers in the monitor which resonate due to the gap in their core upon which the coils are wound. Minute physical changes occurring due to normal warming may cause the gap to assume a spacing just right so the magnetic field sets it vibrating like a speaker, and the gap is of a wavelength that reproduces a high pitched tone. It is in not harmful to the monitor.
As for the speakers themselves, I suspect magnetic induction and/or modulation of the current to them as a result of the conditions described above.
There's in fact quite a number of sources of noise in electronics:
Magnetic fields impinging on ferrous metals (try turning on an old amplifier with a mild steel case, it goes *woomnnngg* from the inrush current through the transformer). These magnetic fields are caused by current flowing through coils of some sort.
One of the more unusual effects i've observed is capacitors "singing" or humming in time with a signal. This is caused by large current fluctuations causing magnetostriction in the dielectric (my word of the day). I had it once in an amplifier, i could sort of hear the music with no speakers attached... right before the cap exploded and splattered me with gunk.
TVs generate a couple of frequencies, but the one most heard within the audible range is at 18khz. I can usually hear it when i enter a house, it's more a "presence" than a sound. I've heard of people who can hear the higher frequency sounds of flourescent lights (not the noise from the ballast). But don't worry, your ears' frequency range drops with age. Fan noise is my pet hate.
If it's really quiet, i can hear the switched mode supply in my palm m105, esp. with backlighting on.
magnetostriction
Set up a loop in a program that can reproduce this noise. Get a microphone and move it around the computer to try and determine where the noise is coming from. Try turning the brightness of the screen down to help isolate the component causing the problem. Once you have an idea which component is causing the noise, you can help determine the cause.
It's not a 100% guarantee that it is the LCD.
- Zav - Imagine a Beowulf cluster of insensitive clods...