Replaced case fans but I'm still hearing rumbling/buzzing noise

[Gandek]

After a bit more than a year of my 2 case fans (exhaust/intake) acting up and making a lot of rumbling and buzzing noise especially during bootups and just normal use, I replaced them both with Corsairs AF120 Quiet Edition (LED) which are pretty popular and recommended fans. After installing these my rig is definitely more quiet but I still notice a bit of rumbling and buzzing but its MUCH MUCH better than the older fans. I want to know whats causing this exactly to completely eliminate the problem. One note to make is that the screw holes for the case fans look pretty beat up and the little plastic parts around the holes look like they are trying to pop off (1 already has from the looks of it) I have a Corsair 300R. I have also made sure that all cables are not touching the fans. Will appreciate the feedback guys

 

-Gandek 

[AlwaysFSX]

They could be vibrating in their mounts which you can fix with these.

[slightlyjaded]

Just now, Gandek said:

 

Have you checked the PSU? You usually do it, by removing it from the case, and booting it up so that the PSU fan can't resonate through the case. Just something to check.

[dfsdfgfkjsefoiqzemnd]

Unplug the case fans while the PC is running (no worries, it won't overheat if you don't actively block all the intakes).  Does the noise persist? 

If it does, something else is actually causing the problem.  Could be the CPU fan, the PSU's fan, perhaps it's actually coming from the graphics card. 

If the noise stops when the case fans are disconnected, try to find out which of the fans is causing it and then mount that on rubbers to isolate it from the case itself.

[WoodenMarker]

If you're running any hdd's, that's probably the culprit. If that's the case, try booting the system up with your drives unplugged to see if that solves the issue.