My power supply is making a weird electrical buzzing sound, it's intermittent and isn't related to the load state of the pc, the same sound is also coming from the other end of the power cable that is attached to an extension brick. My monitor shows interference whenever the noise happens and sometimes I can hear it from one of the ceiling fans as well. The same thing happened about 7 months ago but it stopped after a while. Recently it's been happening again. Note that there isn't any performance issues whatsoever with my pc, just this annoying sound. My PSU has been working fine for 5 years now. It's a Seasonic S12II 520W.