I recently built a new gaming rig using the EVGA SuperNova 650 G1 80+ Gold PSU. When I first booted the system, I noticed a faint humming or buzzing sound emanating from the machine. My friend, who helped me build the computer, told me not to worry about it. It wasn't until a couple of days later that the buzzing noise got a lot louder. It sounds like an electrical buzzing noise. I opened up the side of the case while it was on to determine the source of the sound, and it is loudest when my ear is next to the PSU. I am 99.9% certain it is coming from the PSU and not any other part. The PSU sits on the bottom of the case btw. I've heard the ol' "fan-hitting-a-wire-or-object" noise many times, and it definitely doesn't sound like this.
 
I tried multiple ways to fix it: I turned off the XMP setting on the MoBo (it needed to be on for the higher clocked DRAM I purchased), I tried plugging it into another outlet rather than my surge protector, and I even tried removing the dust cage below the case in order to see if it was the fan. But, the sounds still persists. 
 
The ONLY time I've been able to get rid of the sound is if I completely turn the PSU off using the switch on the back, let it sit overnight, and then turn on the computer in the morning. Then the noise is gone. But, if I leave the PSU switched on during the day and return at night after work the noise comes back. I've tried this twice now.

I'm wondering if anyone else has run into this issue. I'm about ready to exchange this PSU for a new one on Amazon.

P.S.: I Googled this issue more than I can count, and it sounds like this is a random issue that can affect PSUs, and it may have something to do with a faulty capacitor.
 
Here is my setup:
Intel Core i5 6600k
MSi Krait Gaming Z170A ATX 3X Motherboard
EVGA SuperSC DDR4 RAM @ 3200
EVGA SuperNova 650 G1 80+ Gold PSU. 
Phanteks Enthoo Pro Full Tower Case