Hi guys, Would appreciate any help on this. My 2010 iMac had it's optical drive replaced with an SSD about a year ago. I have recently noticed a humming noise that I cannot get rid of. I have tried playing with the fans with 'SSD Fan Control' with no joy. I am assuming it's the internal HDD because when I put the iMac to sleep, the noise goes. Can anyone help get rid of this incessant noise? I am running El Capitan. I have tried a SMC reset but still no joy.