Is my humming noise anything to worry about?

First of all there is not reason to ever unplug the machine when it is off unless there is danger of lightning.

It's hard to answer this type of question as no one here can hear your Mac! 🙂

If it is loud and annoying you I would certainly have it looked at but if it is just a very low noise and everything is running well, I would ignore it. Are you sure it is not the hard drive? Is it possible that it is some sort of noise being transferred to your desk through the foot?

Hey there.

I bought an Imac 24" one week ago and I noticed the same problem as you are describing. When I assembled the imac and plugged in the power plug I noticed this noise as soon as the imac had power. I can't hear this when it's turned on. But when it's turned off or sleep-mode the noise appears. very weird.

The noise stops as soon as I cut the power to it. The noise is not high, only if you put you ear near to the imac. And if there is total silence in the room where the imac is placed.

I had noticed a humming noise associated with my display. Then I discovered it only happened when I dim the display using the the OS X display brightness control. If I leave it at full brightness, it doesn't hum at all. But this is an obvious problem for anyone using a 24" iMac, as it is bright enough to use as a search light.

I am now using the "Brightness Control" program from http://www.splasm.com to dim the display because I found the OS X brightness control doesn't go nearly dim enough for me. When I dim the display using Brightness Control, it never hums, no matter how low I go (as long as I keep he OS X brightness level at maximum).

It seems really strange to me that the OS X control causes hum when set to anything other than maximum (and won't go very dim anyway), yet will never hum when I use Brightness Control, which will go much lower. I don't understand what they do differently.

24" iMac Mac OS X (10.4.8)

YOU ARE A GENIUS!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

You have no idea what I've been going through in trying to solve this issue with my 24" iMac. At full brightness, no humming noise. As I bring the brightness down..BAM, this loud humming noise like a generator starts to appear. It gets louder as I take the brightness lower and lower. I took it an Apple Authorized repair facility. They replaced the whole LCD and Inverter. I bring the machine home, and the loud humming noise is still there. So I bring it to the Apple Store. But the ambient noise in their store is so loud that they can't hear the problem. They decide to order all these parts. I think they believe it could be the powersupply, although they can't even hear the sound I'm talking about. Now I'm suppose to bring in my machine when they call, so they can replace these parts they think might be causing the problem.

Now I read you post in this forum. I download and install BRIGHTNESS CONTROL by Splasm. And...BAM, it works. No humming noise when using this little free application. Thank you very much for posting your solution in this forum!! Very, very smart!

24" iMac/2.33GHz Core 2 Duo/2GB RAM/500GB HD/256MB VRAM Mac OS X (10.4.8) 17" Macbook Pro/2.33GHz Core 2 Duo -- iPod 80GB/Black

It's not loud, it's more the pitch of the noise that makes it a little annoying, and the
fact that I'm sure it didn't used to make it.

I have the same problem with a new 17" imac. When I first got it, I didn't notice any fan noise. Then I did the EFI firmware update, along with some other updates, and afterwards I started noticing the hum. The pitch drives me crazy. I tried the forum recommended SMC reset(power off, unplug all cables and powercord, let sit for at least 15 seconds, plug in cables and powercord and turn back on) several times with no success. I left everything unplugged overnight.

It seems my humming noise is the screen, as soon as the power save for the screen kicks in,
and the screen turns off, the noise disappears.
Is this a normal thing, or is just me?

The exact same thing happens with my imac. As soon as the screen dims, the fan noise stops, but as soon as I touch a key on the keyboard, which powers up the screen, the fan noise starts immediately. I downloaded the iStat nano widget to monitor the fan speed, but my 3 fans always seem to run at the same speed:

fan 2 1000 rpm
fan 1 1200 rpm
fan 0 1000 rpm

Did you get any custom options for your imac? I ordered mine with 2gb of RAM. There are some posts that seem to think Apple technicians occasionally fail to reconnect something after adding more RAM, and as a result the fans always run at full speed.

You could be hearing the hard drive and vibration / noise associated with the drive spinning up. I know mine has a slight vibration / resonance. But no where near my iMac G5.