Was more than a wild guess,that you own a Gigabyte x58!Did a bit of search under the terms "electric buzzes motherboard" and most of them were referring to that specific mobo.
I've found some threads about it, but most relate to whine instead of sparking sounds. Honestly, I don't know how my MoBo is still alive, I hear sparking sounds all the time but no strong smells or smoke, it may shut down or not, but as soon the CPU is stressed it definitely powers down, I was wondering if it was a permanent short circuit on the MoBo it wouldn't even post, what happens is that I can logon to windows and remain on for hours if the CPU is not stressed, totally weird. I can almost bet it has something to do with the VRM, it is either overheating or be overloaded and activating SC protection it makes sense since I can hear the sparking sound. OR it can happen that the new PSU may be faulty, but it is unlikely, I cannot hear any weird noises from the PSU. I wonder if my old PSU eventually damaged something on the MoBo, what I cannot understand is how the machine ran stable for days and suddenly the same problem returns, I haven't touched anything since the problem got fixed.