Hello, new to the forum. I have a late 2015 iMac: 4.0GHz quad-core Intel Core i7, Turbo Boost up to 4.2GHz AMD Radeon R9 M395X with 4GB video memory I noticed a faint electrical buzzing sound that intermittently comes from the bottom left corner of the screen. It happens sporadically, however one way I can reproduce it is by clicking the Downloads icon on the Dock which makes the noise when the icons fan out. I have tried connecting to different UPS units and different circuits and the noise persists. It is definitely not a fan noise, it is more of a high pitch electrical buzzing. Just wanted to see if anyone else has noticed this or if perhaps I have a defective unit. Thanks for any insight.