imac 2021 buzzing noise

Yes it is coil whine. Intensity changes for every iMac. Let's say that there are Apple products with less to no coil whine, whereas in this case it seems to be affecting every iMac M1 out there, to different degrees. I can hear mine in a quiet room but mostly decide to ignore it. No point in having a new one as it could be worse.

There seems to be two issues in this thread that need separating out. The original is far more like coil whine, power/transistor related noise, but further down we're into the high-pitched whine from the display which goes away at full brightness. I've just started the return of my second iMac 2021 because of this high-pitched whine/display brightness issue which Apple Support still claim to know nothing about. Incidentally, as others have pointed out, not everyone can hear it as it's so high pitched, my wife can't unless she really gets close to the display and listens for it, but for me it's unusable.

I do hope they get to the bottom of it and fix it for a future batch, I may try again next August when the student deal is on again!

Yes. Also behind the on/off button. The noise stops when I set the display on maximum brightness.

Tried increasing the brightness and yes, the noise goes away, the moment the brightness is reduced again, it starts right back.

Meanwhile, try disabling Ethernet on the iMac and see if it resolves. The new iMac power supply carries both, power and Ethernet, could be related. Not a solution, but worth nailing down/eliminating.

I got my second unit and it has the same problem like the first one (and the rest of us here). If I lower the brightness below 70-80% the noise is coming up. I think the noise from the second unit is not so loud as the one from the first.

It appears to be connected to power usage. Drawing more power seems to help eliminate the buzzing sound. When I connect my iPad to the iMac (via USB), the sound goes away as the iMac utilizes more power to charge the iPad.

can you also locate it behind the ports?

When most of you hear the noise at low display brightness, it might be a trashy resistor. The power adapter of my razor also makes such a noise. And years ago there was such an issue with Intel notebooks, which was called cpu whining, when the processor decreased its clock frequency.

If that's the case with the iMac, I fear no software update can fix this. I hope this is not a thing, every of the new iMacs comes with. Mine will be delivered in two weeks.

I hope, Apple have a solution with this and replaces affected devices with ones without the problem.

Also it would be interesting, how old are the people, who hear it and how old are those, who doesn't. Young people are able to hear higher frequency noises than older people. Maybe that's why the Apple QA team missed that issue, if it comes with every device.

Same here, it indeed gets louder when dimming the display. I heard from another user the sound should settle in a few days, I don't know if it's true though. I guess people don't wait for their computer to "settle" rather contact apple right away for a replacement. We'll see...

Just a quick update...

While the noise is clearly caused by dimming the screen brightness, I've also noticed that, if the display turns off after some moments of inactivity, the noise persists. It only ceases minutes later, when the computer goes to sleep.

But then again, screen brightness HAS to be low at the point where the screen turns off for the noise to be heard.

It happens the same to me. Apple replaced my brand-new M1 iMac for another one, in this second one the noise is lower, but it's still there. I don't think this sound should be considered "normal" and I hope Apple creates a Service program for this issue.

My 2021 iMac 24 makes the noise, depending on brightness level, and it makes concentrated work frustrating.

The only option is to plug my ears or listen to music.

I have asked Apple for help several times, but since it was after their so called 3 week "grace period" they refused to replace the unit, and repair is not an option, since the problem is not detected by the Apple test procedure.

So Apple considers this issue a non issue, it does not exist, and when I ask for help they act like they have never heard about it.

So I'm very surprised that several people on this board reports that they have had their unit replaced - is Apple support treating people differently depending on region?

Is a known issue in one region not a known issue in other regions?

Bottom line is: I'm stuck with an iMac that Apple refuse to fix, and that is difficult to use for concentrated work - is my only option really to sell my iMac?

I have the same problem. My new iMac gives of a high pitched sound when the screen is below a certain brightness. I think I'm going to contact apple about this...