# Computer making buzzing/humming sound



## Perishingflames (Sep 1, 2008)

Hi,

I've had my imac for under two years, and just recently I noticed it making an odd humming/buzzing sound at times. It's not the normal sound you hear when your hard drive is working hard, it's definitely different. It's not the speakers either, it happens whether they are on or muted.

My suspicion may be that it has something to do with the power. That's because I've been bug testing a mac beta game, and it often crashes my computer, and I have to manually turn off my computer by holding down the power button until it cuts the power.

Does anyone know why this may be and how I can prevent it/fix it?

Thanks.


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## DeltaMac (Sep 1, 2008)

Something mechanical may be making that noise. Hard drive, optical (CD) drive, or one or more of the fans inside. Can you localize the sound (upper back, or bottom edge, where the speakers are?)
You could boot to your Apple Hardware test. It's on the original Disk #1 that came with your system. Boot with that disk in the drive, holding the letter D (for diagnostics) Run the extended test. Maybe the noise will be more obvious with that test, or you will get a failure code of some kind. Post any error code that you get, and someone may be able to help you decide what to do next.
I often will suspect a hard drive, when I hear unusual new noises, especially since you have been treating the drive poorly. Forcing the power off after a freeze is not helping the situation. But, sounds like you have no choice at that point, eh? You should also test the hard drive: Boot to your installer DVD, and run Disk Utility from the Utilities menu. Run the Repair Disk (different from Repair Disk Permissions). If that repairs errors, run the Repair Disk again, until no problems are found.
Come back here with what you find out (if anything)


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## Perishingflames (Sep 1, 2008)

I have just tested both (extended test from original install disk and repair disk from leopard install disk) and both came out clean. No errors.

Any other ideas?


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## DeltaMac (Sep 1, 2008)

The hardware test won't tell you about any noises...
Did you still hear that noise while the test was running?

If the noise is intermittent, then you should try to discover if you can find what causes the noise (when does it happen? Is there some app that you are using when it suddenly starts making noise? Is there anything else that you can say would be distinctive about the noise? Can you make the noise start whenever you want it?

Well, you don't really _want_ that noise, but you should try to get it to repeat, so that some service person can better help you with fixing it...

I have lots of other ideas, but most all will require you to take the iMac in to have someone localize that sound. Or, if you want to try - take the back off, plug in a power cord, turn it on, and try to pin down the exact location of the noise.
If you are not comfortable with doing that, then take to someone who knows what they're looking at.


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## Perishingflames (Sep 1, 2008)

"The hardware test won't tell you about any noises...
Did you still hear that noise while the test was running?"

No I did not.

Thanks for the tips, I will take note when I hear the sound again and try to find the circumstances. Stay by!


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## Perishingflames (Sep 7, 2008)

Hi,

I've heard it again some, it comes and goes at seemingly random times. One update: I was using Windows via Boot Camp, and when I clicked the Shut Down button in the start menu, it just froze up. I logged off with Task Manager, then clicked the Restart button on the log on screen, and it started to restart, but got stuck for 20 minutes or so. Eventually I cut the power, and when I turned the computer back on a couple minutes later, I noticed for a split second before the gray apple logo shows up, I saw a folder with something written on it the same color and basically same size as the apple logo that showed up a split second later.

Is there reason to be concerned?

Edit: I just seemed to notice that the sound comes from somewhere right above the apple logo on the case.


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## DeltaMac (Sep 8, 2008)

Check in your System Preferences/Startup Disk pane. Make sure that your system boot volume is selected properly.

The buzzing/humming sound might be fan. You have three inside. Check the small air inlet located a couple of inches above the power connector on the back. Make sure that cooling air inlet is completely clear.


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## Perishingflames (Sep 21, 2008)

I have a new problem that I think may be related to this. Please see this thread.


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## DeltaMac (Sep 21, 2008)

Your two threads are likely related. I would suggest that your existing problem is simply getting worse. Plan on taking your iMac to someone who can both localize the noise (if possible), and run some other hardware diagnostics.


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## Perishingflames (Sep 23, 2008)

Here's just an update, and new occurance that just happened to me:

http://macosx.com/forums/hardware-peripherals/303156-mac-hardware-problem-perhaps-power-supply.html

Anyways, I guess I should bring it to the Genius bar. Would you recommend that, or can you pinpoint what the issue is better now and recommend a solution (power supply replacement perhaps)?

Thanks.


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## Perishingflames (Sep 26, 2008)

Alright, I brought it to them and they could not help because they couldn't get the sound (its very random occurrence, except when it comes it comes and goes for a while). However, I have localized the sound as you requested in your original reply, and it seems to be coming from the front of the computer, between the center and the left side, more towards the left than the center.

Thanks.
Edit: This may also narrow down what's causing the sounds: The sound was at its extreme, so I decided to shut the computer down, and a few seconds before the screen went black (I was in windows so it had the regular "the computer is shutting down" screen), the sounds just ceased to exist, just stopped all of a sudden. This is odd because normally the sounds fade out and back in often; this time was different. So, I was thinking this would eliminate it being the fans, and stuff like that. Hope it helps (the narrower is that the sounds just stopped all of a sudden, they didn't fade down in volume or anything as I was shutting down).


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## DeltaMac (Sep 27, 2008)

If you shut your computer off, the fans don't slow down, fading away slowly to nothing. Fans will stop immediately during the shut down process.
So, I'm still thinking 'fan'!

You can use something that will monitor your internal temps, and the fan speeds. This will quickly tell you that your mystery noise is a fan (or not!)

I like to use the iStat Pro dashboard widget for that purpose. You can configure the iStat Pro settings to display exactly what you want.
http://www.islayer.com/index.php?op=item&id=7

If your processor is in heavy use, the fans will certainly kick on.
If you monitor your Activity Monitor, choosing to display all processes, then click CPU% in the header line, so the list sorts by CPU%, what processes are at the top of the list? May give you a clue about why your fans kick on...


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## Perishingflames (Sep 27, 2008)

Edit: I used iStat and found that during the buzzing sound, the fan rpm's were much higher than without the buzzing sound. CPU fan was 1071 and hard drive was 1361 *this is the one that seems noticeably higher than without the buzzing* vs under 1000 rpm for CPU without buzzing, and under 1200 hard drive fan without buzzing.


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## DeltaMac (Sep 28, 2008)

well, how about that! Anyway:

Just to answer your question from before your edit, the hard drive fan will be under the middle of the iMac, or to the left. Depends on your iMac model.

If you want to put your Mac under load - try this app - http://geniusx.net/highload/ 
It runs some graphics routines, and randomly launches a variety of apps on your Mac.

Too bad your genius didn't try out Apple's Service Diagnostics. It runs each fan up to speed, then back down. Each are run individually, so a mechanical problem would be quite noticeable.
I think you are just hearing the fan run up - some do make a lot of 'fan' noise, and is likely normal.


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## troy33087 (Nov 11, 2012)

my i mac a1224 makes a buzzing sound when the power is plug in but it wont turn on either


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