27" LED Cinema Display buzz and noise

[Silly John Fatty]

Hello,

I recently purchased a second hand 27" Apple LED Cinema Display, and I now started to have some issues.

The first issue started today, it is some kind of buzz that comes out of the right speaker whenever I lower the brightness of the screen. I have about the opposite happening for other people – whenever the brightness would be above 3/4, a buzz sound would come up. For me it's when the brightness is below 1/4. The lower the brightness, so higher the pitch of the buzz. How weird is that?

The second issue is that, whenever a sound is played, some kind of white noise starts coming from I believe both speakers of the display. Even if I just adjust the volume on the keyboard (which makes a sound as well), this white noise would come up. It would last around 15-30 seconds, and then it would disappear. If headphones are connected to the Mac Pro, it doesn't happen (and it can't be heard in the headphones either). I once hooked up the Mac Pro to a Panasonic TV to test, and there was no buzz coming from the TV either.

Now I just noticed that the white noise is constantly here since the buzz appeared today (when I lower the brightness). Something is failing here I believe. It could also be the graphics card I guess?

Sometimes I get a very quick weird flash on the screen (black & white stripes I believe) for half a second, then they're gone. It's quite rare so it's hard to troubleshoot. Maybe it has to do with the Cinema Display as well. Or perhaps it is my graphics card (It's a Sapphire HD 7950 3 GB – the Cinema Display is connected with Mini DisplayPort). Or it might just be bad drivers for this card – they were never that good apparently.

Perhaps someone knows more than I do

All helps is appreciated…
Cheers!

 

[Ph.D.]

You probably have sensitive hearing and are working in a quiet room.

The buzzing is from internal DC-DC converters (voltage converters and regulation), which involves the use of little electrical coils. These vibrate due to pulsing electrical currents at frequencies within people's hearing range. The tone and volume of the vibrations depends on the electrical load (i.e., screen brightness).

The hiss you hear when sounds come on and off is noise from the audio amplifiers when on and is common in these displays. I consider this a design flaw, but Apple apparently thought it was OK.

My guess is that your screen is probably within normal limits. Personally, I'm also very sensitive to these sorts of noises and they annoy me, but many electrical devices suffer from them. Even my phone's USB charger has a whine.

The screen flash could be many things, perhaps your video card as well, as you say, so I can't help there.

 

[Silly John Fatty]

Thanks. I do have sensitive hearing and yes I work in a quiet room. I wouldn't say it stops me from working (I don't hear it when working, I do music production so it's covered by these sounds) but it worried me that something couldne wrong with the display and that's something I think of all the time, which is very annoying.

What bothers me also is that both the white noise and the buzzing issues weren't there when I received it. Perhaps I didn't notice, but I seriously checked the display when I received it, so yes…

As for those DC-DC converters, I've read around the net that the buzz increases for people when they increase the brightness. Weird thing is it happens for me when I decrease the brightness? So basically I put the brightness a bit higher now all the time to avoid it, because my head thinks it's harming the display less.

 

[Ph.D.]

It's often the case that the power converter whine would get louder with more load such as greater brightness, but not always. For example, the load of the signal processing electronics inside the monitor could vary too. Indeed, moving or changing windows around (like opening a mostly black window) or running different programs can vary the load too. So I would not tie the volume of buzzing exclusively to the screen brightness setting.

Your monitor is fine, or as fine as it's ever going to be anyway. Like I said, I do think that Apple could have done a better job with the audio and even the whine (well-designed equipment often use dabs of silicone goo to dampen the vibrations). I personally hate even tiny sources of electronic noise and, like you, I notice them all!

 

[Silly John Fatty]

Haha, I hope so! It's hard to find these, since I have an old Mac Pro, I can not use the Thunderbolt Display. And when you find some of these, usually they are ****ed up. I don't trust these things, it's like the iMac display, full of problems. But a good display when it works! I was happy when I received mine and saw it had no yellow stitches or dark spots. I'm horrified of this happening. But I guess I'll keep this display forever and just repair it and invest money into it, if something ever goes wrong.

Other than that, in my case, it does have to do with brightness I guess. I noticed the buzz does not only increase when I reduce the brightness, but also when the brightness is automatically reduced, for example by a dark website or such. Or a dark spot in a video. And also, it isn't that it increases, but it's more like the pitch goes up. Weird thing. But I guess it's okay, let's hope these dsiplays will stay alive for many more years to come