Computer making click noise

CPU: Intel Broadwell-E i7 6800K
Cooler: Be Quiet! Dark Rock 3
MOBO: Asus X99 AII
GPU: MSI GTX 1080 8GB X Edition
RAM: Corsair Vengeance LPX 2666MHZ Dual Channel 4x4GB 16GB kit
PSU: EVGA SuperNova G3 850W 80 Plus Gold
SDD: Samsung 850 EVO 250GB
HDDx2: 1TB Western Caviar Digital

Hi

For the past few weeks while gaming, such as BF1 & Killing Floor 2, i hear a click noise from my PC. It sounds similar to when a PSU turns off.

I'm thinking its either the PSU or GPU.

Thanks!
 


Ye my cable management for my pc is clean and so nothing is in the way.

Ye i was thinking HDD maybe as well but wasn't sure.