My roku is making really loud noises. I have the Roku 4. I wasn't watching it at the current time. I have unplugged it for a while and then plugged it back up and it still made that loud noise. I am aware of the little subtle fan noise that it makes from time to time. That sound is kind of like it is winding down. However, this one was louder, like the fan was hitting something or something of the sort.
I have the same issue, like a whirring sound, modulating even when the ROku is not being used. When unplugged, the sound goes away. When starting up it stays calm for a while, but starts making noise in about 10 minutes.