I've researched this and found nothing, but it's also just a hard problem to google.
For the past year or so, my MacBook has been driving me mad by making this whining sound. It's like a holding 'beep' noise; it continues for 1+ minutes until it stops. To be clear, it doesn't sound like anything mechanical. It doesn't 'rev up' or anything – it is whining, or it is not.
It is (usually) triggered by sound. Not by sound actually coming out of the device, because the device can be on mute, but (say) if I play a song, the beeping starts and continues for about a minute after the song finishes.
I've run a diagnostic and it's clean/normal.
Exceptions:
* Right now it's just beeping/whining endlessly.
* I have had it before where is acting completely normal, but when I closed my laptop and reopened it, this behavior started again.
* Sometimes the device simply doesn't play sound unless I plug in speakers, and it seems to be related. However, I have yet to experience this on the new OS.
What doesn't help:
- resetting the PRAM
- resetting the SMC
- plugging in speakers/headphones
- However, plugging in speakers does make the sound emit from the speakers instead of the device. Unplugging them after that sometimes stops the sound until it is re-triggered.
- muting the device
- unplugging the power adapter or other peripherals
- changing the brightness (I have read elsewhere this helped for people)
- restarting the computer has helped in the past, but rarely
I used to be on OS X 10.9, but I just reformatted the device and upgraded to Sierra (10.12).
Obviously this is difficult to diagnose given the exceptions, but it's driving me mad. I now try to find areas of destructive interference so that it's quieter when I move my head there. I can't use headphones anymore because the aforementioned trick doesn't work when it whines directly into the ear.
Any suggestions would be great! I'm happy to try pretty much anything. Thanks!
Best Answer
What you are hearing is either capacitor squeal, or coil noise.
Basically, it's just an audible sound of the electrons as they flow through components and they cause the nearby components to resonate enough to be audible.
Most of the time it's benign, but (obviously) can be really annoying. In the case of capacitors, however, it may also be a sign of an imminent (or recent) failure.
There's a good article describing this: Capacitor squeal & coil whine explained
Either way, if you are under warranty (for any device, not just Apple), you can get it resolved. Even if you are not under AppleCare, I would definately take it in and see what they can do for you.
If you cannot get Apple to service it, have a look at Rossman Computers out of NYC. He has been able to repair what Apple said couldn't be repaired. I am not affiliated with him in anyway, I am just a satisfied client.