High Pitched Noise Coming from CPU when Idle?

Goftrey

macrumors 68000
Original poster
May 20, 2011
1,853
72
Wales, UK
Whenever my MacBook is sat idle, the CPU gives off a really, really high pitched squealing noise. I tried picking up with a microphone but it's not picking up the frequency.

I'm presuming it has something to do with Intel's power management battery saving clock speed magic. But it's driving me crazy. Has anyone else had this issue? Is there any way in which I can disable the idle clock speed changes (if that is actually the issue)?

PS: It happens with or without the MagSafe plugged in.

Thanks.
 

cbautis2

macrumors 6502a
Aug 17, 2013
728
589
Whenever my MacBook is sat idle, the CPU gives off a really, really high pitched squealing noise. I tried picking up with a microphone but it's not picking up the frequency.

I'm presuming it has something to do with Intel's power management battery saving clock speed magic. But it's driving me crazy. Has anyone else had this issue? Is there any way in which I can disable the idle clock speed changes (if that is actually the issue)?

PS: It happens with or without the MagSafe plugged in.

Thanks.
Congrats, you have a good hearing. I used to hear those ultra high frequencies off of my 2011 MBA when idle. Now my hearing is damaged and I cannot hear that noise anymore even though I know that the MBA and another laptop still has that high pitch sound, but only young people can hear it. It's normal and just a side effect of low power CPU states.
 

motrek

macrumors 68020
Sep 14, 2012
2,428
150
Whenever my MacBook is sat idle, the CPU gives off a really, really high pitched squealing noise. I tried picking up with a microphone but it's not picking up the frequency.

I'm presuming it has something to do with Intel's power management battery saving clock speed magic. But it's driving me crazy. Has anyone else had this issue? Is there any way in which I can disable the idle clock speed changes (if that is actually the issue)?

PS: It happens with or without the MagSafe plugged in.

Thanks.
You can download a program called smcFanControl and see how fast your fan is spinning.

I find that my 2014 MBA has a weird resonance (?) when the fan is spinning at ~2000 RPM, which it will spin at sometimes when the CPU is under some load, and it sounds like a much higher and more annoying frequency.

At the default minimum speed of 1200 RPM, I find it inaudible.

You might have some gunk in your fan too (could be cleaned with compressed air?) or a fan bearing that is going out...?
 

Goftrey

macrumors 68000
Original poster
May 20, 2011
1,853
72
Wales, UK
Congrats, you have a good hearing. I used to hear those ultra high frequencies off of my 2011 MBA when idle. Now my hearing is damaged and I cannot hear that noise anymore even though I know that the MBA and another laptop still has that high pitch sound, but only young people can hear it. It's normal and just a side effect of low power CPU states.
Don't know whether to be glad or annoyed! I know on some PCs you can turn various power states off in the BIOS, not sure whether it's possible on a Mac. As it is at the moment it's driving me insane. Trying to type up something in Word with a constant loud tinnitus-like squeal in your ear doesn't do my sanity any good.

I'll either have to find a way to keep the CPU running at a minimum of ~10%, or I could always sell it to an old deaf person! ;)

Thanks for the response.
 

Goftrey

macrumors 68000
Original poster
May 20, 2011
1,853
72
Wales, UK
You can download a program called smcFanControl and see how fast your fan is spinning.

I find that my 2014 MBA has a weird resonance (?) when the fan is spinning at ~2000 RPM, which it will spin at sometimes when the CPU is under some load, and it sounds like a much higher and more annoying frequency.

At the default minimum speed of 1200 RPM, I find it inaudible.

You might have some gunk in your fan too (could be cleaned with compressed air?) or a fan bearing that is going out...?
It's got nothing to do with the fan (unfortunately). The system is dust free, and even with the fan unplugged the sound still persists.
 

motrek

macrumors 68020
Sep 14, 2012
2,428
150
It's got nothing to do with the fan (unfortunately). The system is dust free, and even with the fan unplugged the sound still persists.
I question how wise it was to run the computer with the fan unplugged, since the heatsink is tiny, and the CPU probably got very hot very quickly. Oh well, I guess they are designed to turn off if the temperature gets too high, so you probably didn't do any damage.

Anyway, nothing about the CPU's frequency has anything to do with any noise directly. The slowest it will run is still in the MHz range, which is far beyond inaudible.

If the noise is coming from the motherboard, then it's capacitor whine/coil noise:

http://en.wikipedia.org/wiki/Coil_noise

The resonance is probably dependent on the temperature of whatever cap/coil is vibrating, so when your CPU is idle, the electronics might cool down to the temperature that causes this resonance.

I wouldn't say this is normal. My hearing is excellent and I've had three MBAs and I haven't heard any cap whine from any of them.

Short of replacing components on the board until the whine goes away (which isn't exactly a practical solution), the only way you're going to solve the problem is exchange the laptop for a different one.
 

redheeler

macrumors 604
Oct 17, 2014
7,631
7,364
My late 2008 MacBook Air 1.6 has a similar issue. I have always attributed it to capacitor whine.
 

polee

macrumors 6502a
Jul 22, 2008
583
235
I have a macbook air and do not have this coil whining sound. Perhaps you should bring this to the Genius bar to be rectified. I used to have this on my Toshiba which was running on i3. I think some of the the latest Dell XPS 13 units have this problem too. Just google coil whine and Dell XPS 13 and you will see this issue being brought up in the Dell discussion forum.
 
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