Noisy case fans

[vox]

I find it really annoying when I spend out on so called premium case fan and after a around 6 months the things get noisy. I now have 2 Noctua NF-P12 fans that make cogging noises. That's 2 that will be sent back from whence they came. I've replaced them with some old well used sleeve bearing Coolermaster 120mm fans, what a difference, peace from all that racket. You may know that Noctua supply in line speed adjusting plugs to slow down and quieten them. These seem to make the cogging worse, so it's either air noise or the cogging. I won't be spending loads of money on these fans again.

[Progex]

I like Noctua fans ... they are really quiet ... but will be the same with any fan after 6-9 months use. Dust gets clogged.

The only way is to give your system a clean one in a while. A nice hoover does the job

[vox]

LOL, Good one Max.

The cases I use have very good filters in them and I make a point of thoroughly cleaning these and the guts of all my rigs around every month. What's annoying, the fans are pristine, no fine dust on the leading edges of the blades even.. The two old Coolermaster fans are around 5 years old and were filthy. These were from an old case that a friend was using daily up until a year ago or there abouts. I gave them a good clean and as I said, near silent running on old well used sleeve bearings? Either Coolermaster make really good fans, or the noctua ones are very poor.
Thanks for the tip though, any comments are always welcome. 

[Papa_Shango]

I think those Coolermaster fans will start making a noise soon or might sieze up altogether,  sleeve bearings fans aren't good.   I remember having a motherboard what had a sleeve bearing fan on one of the chips and it gave up the ghost after about a month or so, was a really cheap tacky thing.   Luckily had a spare ball bearing fan the same size and stuck that on it.

[vox]

As the Australians say, "no worries mate" I get an audible and visual warning if any of my fans slow below a pre set limit. I also have some spare 120 mm fans in the loft. I let you know when and if the quit working Papa 

[vox]

I've been experimenting with the noisy Noctua NF-P12 fans. The cogging noise at lower speeds seems to be caused by turbulence. I swapped out the front intake fan on one of my Coolermaster Stacker cases that also has one of these fans and the noise has stopped using the one I changed that was noisy. replacing the the quiet front fan to the side, the noise is back. I can only assume the noise is caused by a cross air flow in the case. I have no idea why this should slowly build up, perhaps its the fan bearings are running in and causing the speed to change ? 
I will try and get in touch with Noctua and see if they have any ideas on this. Maybe it's just the case design ? Any thoughts on this ?