Annoying Humming!

Hi, i know this is an annoying question and people seem to be having similar problems.

My 24" iMac 2.8 4GB Ram is humming relatively loud and sometimes gets louder and other times almost stops for a second and then carries on. Its not to do with brightness as some people have mentioned. Its not to do with my fan speed, ive checked my fan speeds using iStat pro and it seems to be running at the regular speed.

It didnt do this from the beginning i had it for at least 2 months before it began this amazingly annoying noise. It is really too loud to cope with as these kinds of noise drive me mad.

If there is anything anyone can think of before i go through the hassle of getting it picked up and 'looked at' that would be great.

Thanks, in anticipation...

My old friend with a 20" iMac asked me to "fix it" before it drove him mad with its humming. It turned out to be caused by a very slight tilt on the machine because he'd 'anchored' an annoying audio cable under one edge.

Just check that your machine is sitting squarely on its base. Next, check that nothing in the immediate vicinity of the iMac is humming 'sympathetically'. Last, try putting your iMac on a soft cloth.

If none of those simple 'fixes' works, then it would help us to know which precise area of the iMac is emitting the noise, and we can take it from there.

Thanks for your response. I have tried all of the methods you mentioned and none make a difference. If I tilt it back to its fullest sometimes the noise quiets and then goes back to normal. Ive noticed too that if i tap the back of the imac nearest where the sound is coming from it stops the noise momentarily.

The noise is coming from, as im looking at it, the bottom left area. There or there abouts. I hope that helps to narrow it down a bit.

Let me know your thoughts.

Thanks.

Put the iMac to sleep. Can you still hear the humming noise? If it persists while the machine is sleeping, it's possible that it may be coming from one of the fans.

The humming is probably either being generated by the hard drive or the fans. It's unlikely that it's coming from the display although some large LCD displays will emit a low humming noise at times. (Like some fluorescent tube lamps.)

Regards.

mattsuma said:

I've noticed too that if i tap the back of the imac nearest where the sound is coming from it stops the noise momentarily.
The noise is coming from, as im looking at it, the bottom left area.

Click to expand...

Okay, I agree with chsaq that it's likely to be a fan or drive, and I suspect the latter, maybe one of the drive mounts is loose, or a cushioning wedge has worked loose with vibration. Do you shut your computer down overnight, and does the humming resume immediately after startup? [that's to try and determine if expansion with heat causes a component to rub against casing or similar.]

See here: http://www.mac-forums.com/forums/ap...-produced-take-apart-guide-want-feedback.html
(see post #5 for the link). In it you may be able to determine which component inside your iMac is at the lower left of the body.

Maybe some adhesive rubber feet on the machine will be the go to reduce vibration, and hopefully the humming noise. Has been suggested before:-

Apple - Support - Discussions - Is my 1 month old 20" Alum iMac ...

Hi everyone

I've tried the suggestions you have mentioned and it makes no difference. It's driving me insane. Gr.

When i put it to sleep it goes completely silent and when it wakes boom there it is again!

I shut my machine down at night and it resumes as soon as it starts up so its nothing to do with heat expansion or anything like that.

Does the fan keep spinning when the iMac is asleep? I'm not familiar with that model of iMac? In cooler conditions for example, in an unheated room, say 35 - 45°F, would the iMac sleep in total inactivity/silence?

But I suspect the hard drive, which is essentially the only other 'spinning' item inside the iMac, except for the optical drive which is disk-dependent. Hard drives are usually well-balanced, but *maybe* the vertical plane in which it operates is causing it to vibrate excessively. That would be my pick. Tip your iMac gently on to 1) its back and then 2) its front, to see if the humming goes away.

If, after trying all the things that have been suggested in this thread, the humming persists, then it's time to open it up for invasive surgery.

First thing to check if you do have to open it up is that the drive itself is securely mounted with retaining/screws to the frame and/or the cradle and that the cradle, if any, is firmly locked into place.

Sure seems associated with the hard drive!

mattsuma said:

Hi everyone

I've tried the suggestions you have mentioned and it makes no difference. It's driving me insane. Gr.

When i put it to sleep it goes completely silent and when it wakes boom there it is again!

I shut my machine down at night and it resumes as soon as it starts up so its nothing to do with heat expansion or anything like that.

Click to expand...

OK. It's the hard drive which is causing the humming. (The HDD spins down when the machine sleeps but fans continue rotating even when the machine is sleeping.)

If possible, do as Harry advises.

Regards.