Question Fans making lots of noise, but only when mounted in case

yar2000

Prominent
Jul 18, 2019
13
1
515
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Hello everyone,

Around a week ago I rebuilt my PC from a cheap case I got years ago into a nice looking build inside of an O11 Dynamic. I used 6 Corsair QL120 RGB fans, and they look great and worked great until 2 of them started making a really annoying sound today. The best way I can think of to describe it, is that it started to sound like a low-volume turboprop plane (its not loud, but its loud enough to be extremely annoying).

The fans are mounted as a side-intake on my O11 Dynamic. (back of the fans are visible from inside the case, set to pull air in from the right side of the case).

At first I thought there was an issue with the motor, but when I turned my fan speed all the way up in the BIOS, another fan started making the same sound. I experimented with it a bit, and it turns out the sound is only made when the fan is mounted in the case - when I hold the fan in my hand and turn the fan speed to 100%, there is no noise at all. Besides this, the noise also disappears when I hold my hand behind the exhaust area of the fan (again, that is inside the case). Only 2 of my 6 fans do this, and both of them are side-mounted.

This, to me, suggests that it either has something to do with vibrations between the case and the fan or the air passing through something at high speed which makes an annoying sound. Either way, I have no clue how it started and more importantly, how to fix it. I hope someone can help me out because I'm completely lost.
 

yar2000

Prominent
Jul 18, 2019
13
1
515
0
It may be that you just have two excessively unbalanced fans and the case amplifies the effect.
I think the root of the problem lies in the unused fan mounting clips. I just tried his, and when I cover them with my thumb, the noise seems to completely fade even if the fan is at 100% speed. The airflow through that little bracket seems to cause a lot of turbulent air or something, resulting in this noise. Might just try to tape it closed and see if the problem is fixed. Nothing a bit of flextape can't fix...
 

jay32267

Champion
I think the root of the problem lies in the unused fan mounting clips. I just tried his, and when I cover them with my thumb, the noise seems to completely fade even if the fan is at 100% speed. The airflow through that little bracket seems to cause a lot of turbulent air or something, resulting in this noise. Might just try to tape it closed and see if the problem is fixed. Nothing a bit of flextape can't fix...
Or a cable tie.
 

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