I am probably not alone in noticing that any processor makes a high pitch buzzing sound while working, and this sound is more noticeable and varied in pitch when computations are performed. I also hear it from the GPU when doing operations like dragging a window around.

It's not the fan. I also recall a group of hackers at some badass convention recording this noise while gnupg created a key, and got some information about it.

Here it is: Acoustic cryptanalysis

What physical phenomenon produces this sound?

Here are some other reports



  • 2
    Have the pitches make out a song, record it and post it on YouTube; you'll be famous!
    – Brettski
    Commented Aug 8, 2009 at 14:49
  • @brettski: Unfortunately, I don't have a lot of time to waste ;) Commented Aug 8, 2009 at 18:18
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    "badass convention". Is this a convention that is badass, or a convention of badasses?
    – NReilingh
    Commented Feb 4, 2011 at 22:50
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    @nreilingh: it's commutative Commented Feb 4, 2011 at 23:17
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    You asked about "processor noise" and you accepted an answer about other noise. So I don't think you even know if your processor is making a noise
    – barlop
    Commented Jul 23, 2015 at 23:11

3 Answers 3


The most common audible noise coming from computers (besides fan noise, of course) is from the transformers used in the power supplies. They are switched at very high frequencies and they generate a powerful magnetic field (that's how they couple energy from one side of the transformer to the other). That powerful magnetic field is essentially a big electromagnet, so any ferromagnetic material in the vicinity will be pulled towards the transformer and pushed away from the transformer thousands of times a second. Most things are soldered down, but some things (like the windings of the transformer themselves) can have a little play, so they move back and forth at the switching frequency (or a harmonic or sub-harmonic of the switching frequency). This is the most common source of physical noise, and it can be modulated by the load on the CPU (as the current draw from the CPU changes, the magnetic field intensity and duty cycle changes). However the most common source of this kind of noise in this environment is the transformers (sometimes called inverters) used to create the high voltages for the backlight of LCD monitors and TVs.

Since this seems to be a popular topic, I'll add a note on the other big source of noise in PCs. The noise discussed above is produced mechanically, you can hear it without any soundcards or speakers. If you're talking about noise you hear through your speakers, there's another source. CPUs and GPUs use 10s of amps of current from the power supplies, and that current varies depending on what the CPU/GPU is doing. The power supplies typically use the same ground return (usually a copper ground plane layer in the motherboard PCB) that all the other chips (including audio) use. Ohm's law says Voltage (V) = current (I) times resistance (R). An ideal ground plane (made of an ideal conductor) would be zero ohms from any point to any other point, so even 100A of current wouldn't generate a voltage (100 A * 0 ohms = 0 V). But a real-world copper ground plane has some resistance, say 0.010 ohms from one end to the other. So if the CPU current switches between 30A and 10A, the voltage across the ground plane may vary between 0.3V and 0.1V. This means that the ground the audio IC is relying on to "stay still" is actually moving up and down by 200mV. That makes the audio output of the IC jump up and down by up to 200mV (depending on what the processor is doing). Which you hear as noise.

This is a very, very simplified example - people have written books about this topic. I'm just trying to convey the basic mechanism.

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    Ah cool answer. So its small components that basically are vibrating "in time" with the voltage as it goes through the cpu.
    – bobobobo
    Commented Aug 8, 2009 at 16:00
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    Very nicely put.
    – Rook
    Commented Aug 8, 2009 at 21:36
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    +1 for a great answer! I had a Psion PDA which also had a slight whining sound while it was doing heavy work, and even more when the backlight was on -- the sound was evidently related to the power consumption, rather than to the CPU. Commented Nov 19, 2009 at 11:56
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    in one answer on here somebody mentioned a glue gun.. for dealing with noise superuser.com/questions/22683/… not that i'd suggest it
    – barlop
    Commented Sep 10, 2011 at 5:01
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    -1 You do realize he asked about process noise don't you. And you start talking about transformers in power supplies, and (cpu?) noise from speakers, though he thinks(probably wrongly) that he hears it from the unit itself.
    – barlop
    Commented Jul 23, 2015 at 23:11

The Toshiba m40 laptop also used to make this insanely annoying squealing noise. If you plugged in a USB keyboard, the noise stopped.

From here, someone writes about that squealing problem's cause:

The problem is relating to a capacitor that is vibrating probably because there's too much power flowing through it


The power supply of Sony Vaio VPCF series has noise coming from the power supply when it plugged in and you use the laptop. Since the processor's current changes according to CPU usage, the noise changes over time. If you unplug the power supply from your laptop [or the supplier from electricity] you won't hear that sound again.

  • The question asks about a sound coming from the CPU or GPU, not the power supply.
    – Blackwood
    Commented Dec 30, 2017 at 17:49
  • I saw my colleagues and many people asking me about this noise, they're thinking that the sound comes from the processor, but it's just the power supply noise.
    – mhbbbk
    Commented Jan 1, 2018 at 15:09

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