SPCR

Why does my PSU sometimes starts to moo. the noise level gets up and down every second. Is there something broken? Its very random but I have doubts it does it if it gets tooo hot ?

What variety of PSU is it, Fresians are quite well known for being unreliable, they can start mooing the moment you start to use them, if yours is a Highland they are very resiliant to mooing and this could be a problem as they dont usually start mooing for a few years.

If however you have a Jersey, then they do moo but very quietly and you shouldnt really hear it at all, so again this mooing could be a serious problem.

Chances are its the Voicebox thats causing the problem, these can be replaced but you have to be careful of the horns and hoofs, otherwise it might be an idea to upgrade to a very nice quiet Jersey right now.

There is a lot of information available on the net, but for a beginner I would start here.

http://en.wikipedia.org/wiki/Cattle


Andy

Andyb
Now let's be serious for a second. This is a respectable forum and people come here to get their problems solved.

SEM
Have you checked if there's enough water and feed? Or maybe there's too much milk in the udders - that's when teats hurt and mooing is just a way of communicating this. All is not lost tho - get a milkmaid machine, start producing fresh milk - there's always someone around willing to buy fresh out-of-teat milk by the bucket. With today's crappy food full of chemicals, you'll turn a nice profit selling natural stuff.

Time to joke now
What brand is it? How old? What rig do you have? How loud is the, errrr, sound compared to other components?

\,,,/ BOVINE POWER

This problem got magically solved UNTIL I added NF S12 cooler to my Noctua U12F.

So do new propellers have tendency to make humming noise about week when installed. When I first had this hum I had just installed Nexus silent propeller.

One thing I also found out is that when I put pressure on the case (with both hand every side) the humming gets away..... is it somekind of resonance or whatever

One thing I also found out is that when I put pressure on the case (with both hand every side) the humming gets away

sounds like vibration being transmitted to the case. soft-mount your fans (NF-s12 should come w/ fan sticks).

It sounds to me like a standing wave is being created by constructive interfearance.

I had a similar problem with an Antec Sonata II. (Not sure I'd call it mooing , but why not?) It was difficult to isolate the noise because it was coming from literally everywhere. It turned out the factory installed PSU was just a little loose and sent the vibrations mooing through the entire case.

As others have noted, since you can suppress the noise by dampening the panels suggests it's a vibration issue. Spend a few minutes with a screwdriver and make sure everything (not just the PSU) is properly tightened.