This sound makes cooler on the panel. The problem is noise. It will not harm

 

It sounds like something is hitting a fan.

I have checked to see if a fan was hitting a cable or something, but it does not seem to be the case

Since the noise seemed to intensify the closer you got to the pw supply, did you check the pw supply fan OR pull your video card out and see if one or both of the card fans are hitting something?

 

Or maybe the fan in the psu may have some dust build up that is making the fan uneven?

 

Thank you all for your replies.

The power supply fan is not usually running as I put it in "hybrid" mode. I still opened the case to see if something was amiss in it, but found nothing apart from some dust.

The graphics card is quite dusty inside, as well as its fan, but I will need an air spray for it. Should I be worried about the dust inside the case?



Anyway, I found a lid on the motherboard that is of no use to me, and after removing it, the noise seems to have disappeared for good. It was loose on its mount and was located right under the GPU, so that was probably the source of the noise. [EDIT]: Sorry, I was wrong, I can still hear the noise... It seems to come from the GPU.

 

The last picture appears to be a heatsink [probably] for a M.2 drive. If you a M.2 drive, it needs to be installed. Blow the video card out with a can of air and see if you still have the noise.