H110i GT Horrible whirring noise

Hi, i built a new pc yesterday with a H110i GT mounted on the roof of my H440 case. However the fan(s) are making a whirring noise, not a constant hum, but kind of a pulsating sound. It gets worse at mid to high RPMs, but is always audible and very annoying

Here is a clip of what it sounds like and an image of my PC:

http://vocaroo.com/i/s12sUqtatmGa

http://s17.postimg.org/687awvnjj/20160117_021607.jpg

The top radiator isn't mounted using all screw points as it simply wouldn't fit. It's held on by 4 screws, but its still very sturdy. I've tried shifting the radiator along to get more screws in, but it doesn't seem to change the noise.

http://s18.postimg.org/iq5zk3ud5/20160118_165300.jpg

The noise is coming from the left fan on the above images. Could anyone please help with this? im completely baffled by what could be causing it

Hi

To be honest with you, my Corsair fans (that came with my no longer used H80i) are making same noise as they're mounted on top of my case (custom watercool in Air 540).