Has anyone got an answer to annoying hum my 2017 iMac (2tb hard drive,i5) is producing scince I got it only a month ago? Just some background , it a low level hum which directly comes from the unit when the unit is on, the hum only stops when the iMac is in sleep mode. I have already taken it to the genius Bar and was told it's working within spec. In other words badluck it's your problem. I have compared it to other relatively new iMac's and none have this issue. This is my third and maybe my last Mac, as I it's too annoying!