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!