PC buzzing during high graphics gamings - video of noise included

[bcrosby51]

Here is a link to the video I took which clearly has the noise present.
Youtube Link
It is very random, but it happens more when I run a graphics bench test and during extended gaming sessions. I've already tried 3 video cards and it does it with all of them, so I've ruled out that. Any ideas?

 

[bcrosby51]

So, turns out I was maxing out my 600w PSU. I had my CPU overclocked. Once I put it back to normal speeds, the buzzing went aways.