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Thanks. The oscillation (about every second or 1.5 seconds) makes it seem like its related to AC and the PSU. But the sound is definitely coming from much lower than the PSU--near the CPU fans.

If this is normal for the Mac Pro, I think I might just go back to a Dell workstation. At least the fan noise--while loud--doesn't oscillate.

Just as an academic clarification, an oscillation in the 1.5 second range wouldn't be AC related - AC comes in at 60Hz (in the US, I can't say elsewhere) but at 60 times a second, it would sound like a constant hum/buzz. It's two orders of magnitude in difference there - about 0.6Hz vs 60.

That being said, I can't really point to anything.
 
Damn this is horrible. Its not like they are cheap crappy machines.

Could the sound be the ticking or clacking of the ball bearings in the fans when they are turning at low RPM? I have a Sanyo-Denki 120mm fan in my PC and there is a faint chatter type noise as it turns slowly (below 700RPM) which is probably the bearings. As soon as it gets to 900RPM or more, then click is gone. Its very faint but in a dead quiet room, I can make it out. Its not loud enough to bother me though and I'm very sensitive to noise.
 
I got my 2.26 mac pro about a week ago and I couldn't be happier, if I put my ear up to it I can hear a fan other then that silence.
 
I had the same problem on a 2.26 dual. I solved it following this hint.

I finally resolved the issue by installing smcFanControl, and slightly tweaking the fan control speed (I changed the "intake" and "exhaust" from the default speed of 600 RPM to 800 RPM). The problem went away immediately! I suspect the humming is due to the fact that some fans happen to oscillate at the same level / frequency, which is eliminated by the fan speed tweaking.

Downsides:
- the humming noise doesn't go away completely, it remains a little oscillation (10% of the original noise level) in the background
- using smc to get intake/exhaust fans to 800 rpm makes the 2 boost fans going to 1480-1500 rpm (from the starting 1110 rpm speed)

picture_8802.png


Anyway it's a good compromise, I think.
Now waiting for your feedback.
 
I'd just like to confirm that this is NOT an issue with all Mac Pro's.

I got my replacement last night, set it up and absolutely no oscillating hum.

So yeah I now sleep to the nice quiet constant hum of my lovely Mac Pro.

C4.
 
After pulling my 2.8 octo apart a couple of days ago i noticed that heaps of the plastic compartments are placed together by magnets. The magnets are glued to one side of the plastic cases and held together with two magnets on the other side. maybe make sure everything is seated properly
 
I have no idea if you can hear that noise at all - but here you go: recorded with the mic being placed on top of the Mac Pro case.
View attachment 165631

The "ambient noise" is my Mac Pro :D
Its dead silent in my room. ABSOLUTELY silent.

Same sound here, Dragonforce. Seems to be normal. Unfortunately :(

Sounds like a distant sports airplane.

I think Apple has learned a valuable lesson and the 2009 machines are running the fans fast enough (by default) to actually cool the system. My 2006 Mac Pro is dead silent by default and my procs run in the 55c range at idle. My memory is near critical temperatures, and my HDDs often near or even surpass their MOT (Max Operating Temp.) under even moderate loads. So pretty much everything except the processors were running at their highest allowed temperatures and occasionally hit the other side of manufacturer's specs. The procs are 80c max and with Apple's default setting under a full load they very often hit 75c so maybe even we can say the procs too. After me and a few other developers bitched and whined Apple said they fixed this in an SMC firmware upgrade but the system behavior did not change.

So people who knew what they were doing downloaded smcFanControl then only for laptops, patched it and ran it on their Mac Pros. With that installed and running the fans at +1000 RPM ~ 1300 RPM it sounds exactly like the recording you made. If we take a look at the 2006 ~ 2008 cases and mountings it's not really intended to be a silent case design. Nothing is rubber mounted, there are no fan baffles, and all interior surfaces are shinny hard metallic. So a Mac Pro when properly cooled should sound just about like that recording. My 2006 Mac Pro certainly does. :) In fact with my audio amplifier turned up pretty loud your recording was so identical to my system that I couldn't tell if you had actually recorded anything till I set my fans back to their default speeds.

So, I would say Apple finally got it and your system will run cool, long, and trouble-free for many years to come. Thank you Apple.
 
I just got my 2.66 (2499.00) and it hums also.
Thinking about returning it and eating the 10%
 
Okay, seriously now... I do have some noise with my Mac Pro, but most of it is coming from the Blackmagic Decklink that is installed. When I stop the Decklink fan, it's just a real quiet purr.
I also have a slight buzz coming from the area of the psu (top rear). I've read that this psu buzz can result from dimmer switches on the same power circuit, flourescent lights and energy saver bulbs. I have a few dimmer switches on the circuit so this may be it. Some posts have mentioned back-ups providing a less than perfect sine wave which may contribute a buzz.
Another explanation I have read about is that the ribbon cable for the PSU contacts the psu fan housing, the vibration from the fan against the ribbon cable causes the buzz sound. I'm not going to investigate this at the moment, because I can't hear my psu buzz over the Decklink fan.
 
Blackmagic Design kindly sent me a replacement fan which arrived today. I did the swap and now my '09 MP 2.26 octo is purring almost imperceptibly.

I do still have a little PSU buzz if I get my ear right down next to it. But I think this would qualify as whisper quiet. Just a soft purr.

I think my PSU buzz is from dimmers because I have several on the same circuit.

Was anyone else's buzz/humming resolved?
 
Just got my replacement MacPro today. The new one has no humming noise anymore :). I am glad to have a quiet MacPro. Now, if the 24" LED ACD had a longer cable, I could put it on the ground instead of my desk. That would make it even quieter.
 
New Mac Pro coming

I got fed up with the noise and called support today. I asked them to ship me 2 new fans for the processor cage so I could try to get rid of the noise.

They didn't want to do that. So they are shipping me a replacement machine. I will report with the noise results once it arrives.
 
My mac pro noise reason establishing and fixing some.

My new 2.26 octad mac pro was very noisy.

1. Massive low-pitched fridge-like vibrations - very annoying;

2. Optical drive low- and mid-pitched vibrations and high-pitched resonances;

3. GT120 mid-high-pithed hum - rather loud, but not annoying due to uniformness.

4. PSU buzz and purling (like electrical breakdown or electrical arc) - rather quiet.

As for 3. Obviously it can be fixed by replacement videocard by quieter one (they say some flashed 8800GTX are most quiet macpro's videocards ever - any suggestions or variants?).

As for 4. I noticed that it depends on power cable spatial positioning. In several positions buzz and purling are almost gone.

As for 1 and 2. I noticed that fridge vibrations problem relates to fans, mostly to intake and exhaust. And it is possible to lower it by setting fan's speed to some values. However I stopped these fans mechanically but fridge-noise left. Likely this hum problem depends on intake and exhaust fans frequences, but relates to whole system "Case <-> All of the fans". This system have it's own resonance frequences. So I tried to find places which resonate heavier. I inspected mac pro and noticed couple of crappish chinese assembling ****ups:

1). retention bar and pci fan was not fixed.

2). (most horrible) As you know, optical drive bay has slits on its bottom which have to be slided along the screws. But in my case optical drive bay's slits was not putted on screws. Instead of this it was placed over screws. and pushed in by brute force. In place it was not fixed and was vibrating. But it was very hard to take it out because it became jammed if I tried to pull it out.

After fixing 1 and 2 all vibrations, resonances and low-pitched noises became quieter, but have not gone. Tried some smcFanControlling (Intake ~700 and Exhaust ~650, not remember exactly, I'm at other computer now) and it have almost gone (now it is uniform, very quiet and almost unperceptible like healthy mac pro).

The most loud part of my mac pro now is GT120 fan noise.
 
Hmm, this sounds rather like shoddy workmanship. I knew as anyone would by looking, that the Mac Pro case design had zero consideration for noise suppression but you're saying it's even worse than that huh? Wow.

BTW, if you need a really quiet system there's quite a bit you can do yourself to lower it. I don't mean the "fixes" that blinkfrog did. I mean like rubber-mounting everything (screw changes), adding silicone plastic strips to the drive sleds where metal would be touching metal, replacing all of the fans in the system with quieter ones, or even changing the actively cooled parts to silent water cooling. If this seems like a lot of work it's really not. If you need this kinda silence but don't want to modify your mac then there are silent fan cooled cabinets you can buy to place you Mac Pro into.
 
Man! Buzzing Psu + Fan in the Nehalem Mac Pros. 15" and 17" unibody macbook pro having flickering screens issues.

Aint no happiness no where~
 
Please help!

I bought the dual processor 2009 Mac Pro last week. As I wanted more RAM it was BUILT TO ORDER for me - late June 2009 - assembled in Ireland and purchased from a premium dealer in Europe. Serial starts with a "CK"...

I am having the exact same issues as described by others in this and many other threads - "fridge humming", "propeller airplane in the distance", "low pitched oscilating", "diesel engine" etc. I can also feel the chassi vibrating slightly.

Prior to purchase I had been reading about this issue and I was hoping Apple had a fix for this as late as June. All in all, it's an issue I don't want as it's very annoying when you want to work in a quiet room, mix audio and/or record. I have owned three tower Mac's prior to this one. The G4, the dual G4 mirror and the dual G5. My experience is that its noise is somewhere between the G4's and the G5 in terms of annoyance - i.e. pretty annoying. The G5 I actually thought was much less annoying although it moved more air...

I was wondering what my rights are in terms of getting this computer mended or replaced - getting it as quiet as the 2008 Mac Pro's - which I think are really good in terms of noise?
 
My 2006 mac pro had a weird hum. After going over it, i would press on the side or top and the noise would stop. The hard drives are not totally tight in there either. My 2008 is dead silent. One thing weird is I replaced the hard drives with hitachi drives and the noise/vibration is gone.
 
These last two posts make me think that Apple is buying fans from a supplier that is producing unbalanced fans.

HQ Fans are like $20 a piece. You can test this by changing the fan speeds and see if the noises (pitch etc.) also change. If they do then that's it! So it's just $100 to replace all the fans in an octad 2009 with HQ ball-bearing, fluid, or maglev silent running ones. I guess it'll take about an hour to do all of them. Might be fun too! Some HQ fans come with pretty multi-color LED illumination too. :D
 
I installed a fan controlling software and increased the fan speeds. The speed and pitch increases and the sound becomes even more appearant. I'm pretty sure the fans are unbalanced. I went down to the store today and put my hands and my ear on the 2008 mac pro's. They weren't vibrating or humming at all, even pressing my ear against the chassi... I only heard the "air" sifting through the machine.
 
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