My iMac has been making an irritating static crackling sound for a while now.
Under advice, I reset the SMC, and after a period where the machine wouldn't start up at all, it then did and the noise was gone.
Two restarts later and it's back.
OS was also updated under advice.
Any ideas?
Try plugging the iMac into another electrical outlet on a different circuit without any surge strip. Best to try it in another room.
Try running the Apple Diagnostic. Do you hear the noise while it is running?
Try an Option Boot. Just after pressing the power button, press & hold the Option key until the Apple boot picker menu appears. Do you hear the noise at the boot picker menu without any OS running?
If you hear the noise with either of these two options, then you will need to have the repair center examine the iMac again for this noise as it will be a hardware issue. If the repair center is unable to hear the noise, then perhaps the iMac is reacting to an electrical issue (dirty power, too low or too high voltage, etc.) or a wiring issue in the home.
Try plugging the iMac into another electrical outlet on a different circuit without any surge strip. Best to try it in another room.
Try running the Apple Diagnostic. Do you hear the noise while it is running?
Try an Option Boot. Just after pressing the power button, press & hold the Option key until the Apple boot picker menu appears. Do you hear the noise at the boot picker menu without any OS running?
If you hear the noise with either of these two options, then you will need to have the repair center examine the iMac again for this noise as it will be a hardware issue. If the repair center is unable to hear the noise, then perhaps the iMac is reacting to an electrical issue (dirty power, too low or too high voltage, etc.) or a wiring issue in the home.
What is the exact model of your iMac? You can get this by clicking on the Apple menu and selecting "About this Mac".
Have you tried muting the speakers to see if the speakers are the source of the noise or if it is a hardware issue.
How loud is the noise? Is it loud enough to hear over a gentle conversation, or do you need to put your ear up to the enclosure to hear it?
In addition to the questions that HWTech asked, could you also provide the following:
Does the noise vary in intensity? If yes, when?
If you put the iMac to sleep can you still hear it?
Does the noise change if you change the brightness on the display?
Are you able to pinpoint the approximate location where the sound is coming from? (e.g. bottom left corner of display, middle, upper left corner of display)
hi,
its a 27” iMac, late-2015, 3.2 GHz Intel, 5k retina.
its definitely not speaker related.
in my unofficial opinion, i would have said it is likely to be hardware, but the fact that for one brief login period after an SMC reset the noise wasn’t there, that seems to throw that into doubt, no?
i took it to a Genius Bar between the time of the SMC reset before it was able to turn on, and they said maybe logic board. that felt like a default answer.
not it sure if the ‘not turning on for a few days’ after SMC reset is an issue linked to the noise, but both are equally tedious!
hi there,
it’s loud enough to be irritable. i’ve got mild tinnitus already so can just about ignore it - my wife can’t stand it though.
it comes in almost immediately after pressing the power button, so while the screen is dark.
it doesn’t stop when immediately put to sleep, when the screen goes dark, but as the machine eases to sleep, so the noise slowly fades out. although the odd faint crackle occurs thereafter.
as soon as a key is hit to wake it up it’s back as before, crackling away.
seems like it’s a little stronger from the bottom left, but essentially it carries right across the bottom.
haven’t noticed it vary in volume too much, although maybe it is very slightly quieter since coming back after SMC reset and subsequent restart.
brightness setting has no effect on the noise.
i’m winding up for the day as i’m in the uk but will check in tomorrow - hope the details supplied are clear enough.
thanks, Alex.
hi,
thanks for the troubleshooting tips.
it followed a similar pattern as before - having unplugged and plugged in again (in a different room this time), it wouldn't turn on for a few hours.
then when it did, there was no noise - but then when I restarted, it's back.
and it was there as soon as powering up regardless of running Diagnostic or Option boot.
maybe I'll try it in a different home to finally check if it's a power/wiring issue at home?
otherwise, as you say, it's clearly a hardware issue.
thanks, Alex.
hi there,
it’s loud enough to be irritable. i’ve got mild tinnitus already so can just about ignore it - my wife can’t stand it though.
it comes in almost immediately after pressing the power button, so while the screen is dark.
it doesn’t stop when immediately put to sleep, when the screen goes dark, but as the machine eases to sleep, so the noise slowly fades out. although the odd faint crackle occurs thereafter.
as soon as a key is hit to wake it up it’s back as before, crackling away.
seems like it’s a little stronger from the bottom left, but essentially it carries right across the bottom.
haven’t noticed it vary in volume too much, although maybe it is very slightly quieter since coming back after SMC reset and subsequent restart.
brightness setting has no effect on the noise.
incidentally, the machine has had only mild internet browsing and Apple Music use in 3 years of owning it. most working files are saved to a NAS so there’s plenty of free RAM, and we tend to use work MacBooks to use any applications.
i’m winding up for the day as i’m in the uk but will check in tomorrow - hope the details supplied are clear enough.
thanks, Alex.
iMac static/crackling sound bottom of screen
