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Why Does a Screen Re-Draw Make Noises? 236

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?"
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Why Does a Screen Re-Draw Make Noises?

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  • Static electricity? (Score:2, Informative)

    by EvilMal ( 562717 )
    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...
    • I noticed the same years ago, and assumed it was static, just like the noise a TV tube makes when you switch channels. I never heard any noise with an LCD screen, and i think the OP migth be experiencing some psychological rather than real effect. Or has anyone else heard an LCD screen make noises?
      • Yes. I've had laptops that made sounds when
        significant screen blits occurred. In particular,
        a Dell Inspirion 5000e uxga. That's an ATI Rage-M
        video chip. As I recall (my daughter has been
        using it lately), I only heard it with XFree86,
        not with Win2k, and it sounded like it was composed
        of a lot of rapid chirps or clicks (~50 msec),
        but had a principal harmonic in the kHz range.
        • Same thing but on an XGA Dell Inspiron 4000 with same video chip (ATI Rage-M). I can also hear the same things on heavy memory operations like kernel compiling (of course the hard drive has to be somewhat silent).
      • by Mad Quacker ( 3327 ) on Thursday February 27, 2003 @03:23AM (#5393984) Homepage
        Just to add to that, 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. The channel changing sound is much lower pitch so almost anyone can hear that, not to mention the static discharges that can occur. It's no surprise to us that electronics make noise, in fact sometimes it can be downright painful. I used to have this 32" inch TV that would whine to the point of pain until it warmed up 5-10 minutes later. Of course as I cover my ears everybody else doesn't notice a thing. Good ears can be a curse :(
        • I can hear that too. I can tell if a TV's on nearby - in another room or even downstairs. Always have been able to, although it was much more noticable when I was younger. High frequency devices are less noticable though. What about the details on screen? I find that a white screen makes a higher-pitched noise than a blank one. On another note, my old monitor used to make high-pitched noises every so often which could be solved by giving it a sharp whack.
        • by unitron ( 5733 )
          That high pitched whine isn't the CRT itself, it's the audible result of the laminations of a transformer core expanding and contracting under the influence of the current, which is varying at the horizontal sweep frequency, in the transformer windings. This expansion and contraction is called magnetostriction.
        • 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

          Yes, but considering that the "extremely high-piched whine" of a TV set is around 16kHz you really don't need exceptionally good hearing to be able to sense it.

          OHOH, I'm pretty sure nobody can hear the scanning frequency of an average computer monitor. That's because the horizontal scan rate is too high to be heard. Note that some other noises that come out from your monitor are still possible. Usually those are generated by a poor quality power supply.

          If you have a TV that makes that whining sound you can get it silenced by getting its deflection coils re-lacquered.

        • I addition to that, I can hear my fanless router work. It makes little teeny buzzes and clicks whenever there's data pumping through it. Strange.
        • Give me some of your curse, I can't hear anything over 11 kHz :\
        • 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
        • there are quite a few people that can hear the extremely high-pitched whine of CRT's scanning

          I am so glad to hear you say that... though a little sad at the slight loss of uniqueness. My sister and I have always been able to hear TV set electronics. If someone has the windows of their house open, I can hear their TV electronics from out on the street, sometimes as much as 100 feet away.

          I can also hear the LCD display on my digital camera if I hold it a few inches from my ear on a quiet day. I'm used to hearing various operating sounds from my computer (and computer monitor), to the point that I sub-consciously que myself based on the sounds the computer makes.

          The most startling effect that I've noticed came once when I was in the Navy. I was sent to wake up the shift relief one night. I walked into a darkened sleeping compartment and walked over to where I knew the relief was sleeping. I could hear his headphones playing in the dark. When I awoke him, I had a strong impression of the headphones rising as he lifted his head, then *turning towards me*. I could actually tell when he turned his head in the dark!

          I'm also fairly sensitive to low-frequency sounds. In the past, I have been able to tell the location of automobile engines several yards all around me, but I am now finding myself alarmingly deaf--sometimes, I don't notice a car until it is right in front of me. I don't know if the engines are getting quieter or I'm going deaf.

          I managed to maintain my hearing through 2 years working in the engine room of a US Navy ship. However, 2 years of driving a wind-noisy car at 70 mph has nearly destroyed my high-pitched hearing in my left ear. I can no longer tell direction of the TV sets that I can still hear well with my right ear. BTW, I'm about 37 years old.

      • by You're All Wrong ( 573825 ) on Thursday February 27, 2003 @04:35AM (#5394245)
        LCD actually change physical state, i.e. there is a mechanical change. Enough of those at the same time, and there will be some sound. A little like piezo-electric shriekers, but much smaller, and with much smaller movement, and only a single pulse of movement rather than repeated oscillation.

        My Psion 5 used to sing a merry song to me all the time as things changed on screen. Almost everything LCD makes these noises in some quantity. I do have very sensitive ears though, so perhaps not everyone hears them.

    • If it's anything like my laptop experience, it is
      most notable when you drag a window with redraw on.
      It's quiet, but very clearly perceptible in most
      environments (not on a passenger jet in flight,

    • Hehe, for things that (mainly) don't have speakers monitors sure make some strange noises eh?

      I've got ones that fart, crackle and squeal. Everybody! Degauss on 3..2..1..

  • In my 3D grafix programming life, i never heard these noises :)
  • Electromagnetism (Score:5, Informative)

    by Mad Quacker ( 3327 ) on Thursday February 27, 2003 @02:51AM (#5393831) Homepage
    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.

    • Re:Electromagnetism (Score:5, Interesting)

      by Smidge204 ( 605297 ) on Thursday February 27, 2003 @08:42AM (#5394865) Journal
      I wasn't aware that humans could 'hear' electromagnetic waves. :)

      The reason transformers hum is because their cores are vibrating in response to the magnetic fields they're subjected to. Same with flourecent lights (which have transformers in them).

      But yeah, just about every AC power appliance gives off a "Hum" of electromagnetic waves, and digital devices, with their constant pulsing, do it as well. And preventing the two from interacting is big business.

      Some good examples from personal experience:

      Trying to record some audio clips, but when I play them back, half of them have a STRONG buzz in the background. So loud you can barely hear the recording. Turns out my mom turned on her ceramic kiln in the basement (which sucks a lot of juice), creating strong interference. Sure enough, when the kiln turned off, the problem went away.

      If I have the volume up, not only can I "hear" the screen redraws, but the mouse move, my keyboard pulse, and my network card go to work. If I have the headphones on and the volume all the way up, I can hear the hard drive working, too. (Interestingly, I'm reminded of this one government "safe room" that was specifically sheilded to stop these pulses, since it would be possible to catch and decode them to figure out what the input devices are doing. eg: passwords and other text)

      • More than one room -- I believe every US embassy has such a room, shielded to the extent that only battery power is used inside. No holes in the Faraday cage once the door is closed.

        I have no idea what they do about air. Perhaps a baffled air duct can be used, or maybe they just work quickly. :)

        • Or perhaps just a copper wire screen over a regular air duct? A Faraday cage does not have to be solid to be effective.
          • Looks like milspec gets tougher than screen, judging by this, [] which describes a honey-comb waveguide approach. (That company also makes welded steel rooms, with no fasteners used in the seams -- just solid steel everywhere.)
      • ---snip
        If I have the volume up, not only can I "hear" the screen redraws, but the mouse move, my keyboard pulse, and my network card go to work


        Or your algorithm finish...I used to leave my stereo next to my apple ii; when I had a calculation that was going to take especially long to finish running (plotting fractals at hi-res was a favorite), I'd crank up the stereo on a frequency that picked up the activity well. When the machine was performing a complex task, the sound was very white-noisy. When the machine finished and went into a loop polling the keyboard memory location, the sound was a buzz. I could be in the other room and know when things were done, or in some cases know how _soon_ it would be done. :)

        Great, now I'm starting to feel homesick for that old machine, and I'll probably end up unpacking it this weekend (again). Some things an emulator just cannot replace.
    • by Sentry21 ( 8183 ) on Thursday February 27, 2003 @09:29AM (#5395068) Journal
      It's the same reason electrical transformers hum

      Because they don't know the words?

    • BTW I've found it often helps a lot to change the hertz of a monitor to get rid of most of the buzz. But I've NEVER heard a buzz from a CRT, thats just weird, you must have very sensitive ears.
    • I've come up with a similar but not identical explanation: I've heard this on a laptop without speakers. I hypothesised that the currents when moving windows created a regular enough change in charge on some circuit traces that were close to the case, and that the inductive change was causing the AIR around the circuit board to react. All you need is some ions and they should react to the electric field.

      My guess is that the net fluctuation of a computer is pretty random, and hence isn't percieved as noise by humans, but when moving a large block of bits around, there's enough repetition or constructive interference, or some sort of harmonic interaction *waves hands furiously* that allows the net interaction with air to be heard as sound waves.
  • Hrmmm (Score:1, Insightful)

    by Anonymous Coward
    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:
  • 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.
  • by Anonymous Coward on Thursday February 27, 2003 @02:53AM (#5393841)
    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.
  • by orthogonal ( 588627 ) on Thursday February 27, 2003 @02:59AM (#5393871) Journal
    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


    Yessssss. Yesssssss. Kill the hobbitses!
  • experiment (Score:3, Insightful)

    by Lord Bitman ( 95493 ) on Thursday February 27, 2003 @03:09AM (#5393906) Homepage
    have you tried turning /up/ the volume of the speakers?
    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 /internal/ speaker?
  • 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.
  • by Bastian ( 66383 ) on Thursday February 27, 2003 @03:17AM (#5393949)
    or at least get them from the grocery store instead of collecting them out in the forest.

    That should solve the problem quick.
  • by toybuilder ( 161045 ) on Thursday February 27, 2003 @03:22AM (#5393977)
    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.

  • 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... ;)
    • by Scorchio ( 177053 ) on Thursday February 27, 2003 @06:21AM (#5394512)
      Presumably you're refering to this event at the Homebrew Computer Club back in 1975... (snipped from this article [])

      The Altair may have been frustrating, but it drove the nerds to experiment, finding real uses for the useless box, turning it from a curiosity to a computer.

      Lee Felsenstein
      Steve Dumpier set up an Altair, ehm laboriously keyed a program into it. Somebody knocked a plug out of the wall and he had to do that all over again but nobody knew what this was about. After all, was it just going to sit and flash its lights? No.

      Roger Melen
      You put a little eh transistor radio next to the Altair and he would by manipulating the length of loops in the sofware - could play tunes.

      Lee Felsenstein
      The radio began playing 'Fool on the Hill'....Da da da, da da da....and the tinny little tunes that you could tell were coming from the noise that the computer was generated being picked up by the radio. Everybody rose and applauded. I proposed that he receive the stripped Philips Screw Award for finding a use for something previously thought useless. But I think everybody was too busy applauding to even hear me.

      Roger Melen
      It was a very exciting thing, it was probably the first thing the Altair actually did.

      On a related note, my old BBC micro used to pick up interference on it's internal speaker, which could actually be used for some basic debugging. You could tell if it had crashed, or whether it was still running round a particularly heavy maths loop, etc...
      • I was reading a history of computers, and how devastated the programmers were at the first vacuum tube (as opposed to relay) computers. See, the vacuum tubes were silent -- how were they going to debug their programs?

    • Somebody should write an app that plays one-channel melodies with the RF noise... ;)
  • BOFH: (Score:5, Funny)

    by Eneff ( 96967 ) on Thursday February 27, 2003 @04:07AM (#5394158)
    *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.


    Luckily, this is something you can quiet fairly easily. Do you have a screwdriver?
  • Solution (Score:5, Funny)

    by D.A. Zollinger ( 549301 ) on Thursday February 27, 2003 @04:26AM (#5394222) Homepage Journal
    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!

  • Noise.... (Score:5, Funny)

    by keoghp ( 457883 ) on Thursday February 27, 2003 @05:08AM (#5394345)
    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.
  • Oh man, me too (Score:2, Interesting)

    by eamonman ( 567383 )
    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 ;)
  • Singing Capacitors (Score:2, Informative)

    by Anonymous Coward
    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.

  • 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.

  • by Gordonjcp ( 186804 ) on Thursday February 27, 2003 @07:56AM (#5394741) Homepage
    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.
  • Crappy hardware (Score:4, Interesting)

    by jfunk ( 33224 ) <> on Thursday February 27, 2003 @08:31AM (#5394826) Homepage
    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.
    • Re:Crappy hardware (Score:3, Informative)

      by shepd ( 155729 )
      You got an MSI for a reason.

      From my experience, here's what I've found as to why to buy from different motherboard manufacturers:

      Soyo: A value board. Lots of stuff crammed on for a good price, or hardly anything on it for a bargain basement price. Not a bad board, but not top notch.

      MSI: The die-hard motherboard. Might not be a cadillac, might even have some annoyances, has no luxuries at all (usually), but dammit, they _always_ work, and are reasonably priced.

      Asus: The "high-end" motherboard. Just like cars, where more money gets you some bells and whistles, but not always more reliability, Asus motherboards are bought by people trying to show their box is "awesome" because it cost more. If you look past the pricing, quite a good board. Lots of support, too.

      ABIT: The ricers mobo. ;-) Designed for overclockers, with the stability overclockers (not sysadmins) expect. Usually the higher cost for these boards nullifies overclocking benefits, but just like people who add "Type-R" stickers to their cars, the people buying these boards don't care.

      PC Chips (aka any weird Chinese name you can think of): When cheap-enough (Soyo) isn't. Zero support, stolen/fake parts, and a high failure rate. But look at those prices! Often found in low-end Brand Name machines.

      ECS: PC Chips "top-notch" line. A well supported stolen/fake parts brand motherboard.

      A-Open: Overall, pretty good stuff. Good in most categories (price, support, quality, performance) but fell out of favour with after providing me with a broken BIOS for an old board, ruining it (didn't have an EEPROM burner at the time). Definately not an overclocker's board.

      Shuttle: Haven't had enough experience with their product. Boards I have seen were reasonable.

      Tyan: Haven't seen too many of these boards, but people I know tend to regard them as a good for a frankenserver board.

      There's others (gigabyte, biostar [pc chips?], intel, DTK, etc) but I simply don't see these boards in operation much anymore.

      So that's why they sold you MSI. You came in telling them your board was causing you hell, so they gave you the bulletproof one. I'd have reccomended you to stick with it and buy a PCI sound card (heck, if it were my store, I'd probably just give you a used SB PCI128), but hey, that's just me. Then again, I'd have replaced your board with an MSI with the Nforce2 chipset, so you'd have decent sound to start with.
      • So that's why they sold you MSI. You came in telling them your board was causing you hell, so they gave you the bulletproof one. I'd have reccomended you to stick with it and buy a PCI sound card (heck, if it were my store, I'd probably just give you a used SB PCI128), but hey, that's just me. Then again, I'd have replaced your board with an MSI with the Nforce2 chipset, so you'd have decent sound to start with.

        The SB PCI128 doesn't have a real digital output. The store I bought from had one SB with SPDIF, and it was $300. To replace one function of a $250 motherboard with that is absurd. On top of that, I would have had to plug it into the front of my box. That's just ugly.

        You're not getting my point, either. The sound was noisy as hell at low volumes, where my Soyo is virtually silent.

        Other problems (Offtopic):
        • The board had two IDE interfaces, even though I told the guy it had to handle 5 IDE devices
        • It didn't detect or use RAM properly. I had to manually set the RAM timings in order to get it to boot without crashing
        • It crashed during heavy AGP transfers

        I checked out comments about the board on the LKML and everyone agreed that it was a POS. That was enough for me. I brought it back and I now have an ASUS on the way.
    • Properly designed hardware should not do this. Tell that to Apple - My iBook has done this since day one.
    • Does it happen when you move your mouse? Turn of sound input under "AUX" and/or "MIC", "LINE", etc.
      Sometimes they pick up noise and rebroadcast it through the speakers - I've had lots of soundcards and boards that do this.
  • 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.
  • iMac too! (Score:2, Interesting)

    by gabe ( 6734 )
    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.
  • Inverter. (Score:3, Insightful)

    by ahknight ( 128958 ) on Thursday February 27, 2003 @09:51AM (#5395212)
    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.
  • RF noise (Score:2, Interesting)

    by halfelf ( 646037 )
    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!"
  • 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.
  • Wow!!!! (Score:5, Informative)

    by FreeLinux ( 555387 ) on Thursday February 27, 2003 @10:32AM (#5395468)
    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.
    • Somebody who hasn't been censored by slashdot, please
      mod this guy up.
    • Re:Wow!!!! (Score:4, Insightful)

      by drinkypoo ( 153816 ) <> on Thursday February 27, 2003 @05:01PM (#5399913) Homepage Journal
      I think you're probably wrong. I think it's far more likely that the sounds being heard are related to the power supply of the monitor. We all know that monitors make a number of sounds during normal operation and that they have a lot of high voltage inside of them.

      You can DEFINITELY hear sounds of this nature (during screen redraw) come out of the speakers of many older computers. I had this issue with my Amiga.

      If the noise is actually originating in the video card, it's probably due to poor design in terms of RF, and the noise is probably being put out onto the ground of the motherboard, and thus transmitted to the sound card.

      • I missed the part about the speakers being disconnected. I'm going to go back to betting on the monitor's power supply making the noise.
    • by nito ( 1314 )
      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.
  • 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).

  • If you... (Score:5, Funny)

    by psyconaut ( 228947 ) on Thursday February 27, 2003 @10:55AM (#5395669)
    ...bury you TiBook in the forest and leave it there....does it still make screen redraw noises? ;-)
  • 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...)
  • From [],
    The noise (hum) In a conventional transformer Is due to core magnetostriction, which is a very small deformation of the core iron under the influence of the magnetic field induced by the AC primary current.

    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...
  • 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.
  • 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.
  • 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... 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.

  • 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: _t roubleshooting.html

    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.
  • Mousing noise? (Score:2, Interesting)

    by BillX ( 307153 )
    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?
  • 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 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?

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