G5 chassis drone, hum?

It's been driving me nuts for the past 3 months now. When the fans are constantly idling and can vary from 10 minute to an hour the side panel door latch starts to drone/hum in cycles.

Anyone encounter it at all? it's very annoying when sleeping. Sometimes I have to wedge a bit of foam behind the lever to stop it. Sometimes it comes back and have to open the lever to stop it as well.

It seems to be a build up, mm break, mmm, break, mmmm, break. Though upon inspecting, funny that the lever mechanism is inline with the optical drive...

The hard drive in bay B was the partial cause of it. After all these years I never knew Apple supplied the rubber covered screws for the drive with the 4 lined up on the plastic fan holder. Originally used regular curved hard drive screws but they worked fine before until now. God knows how I missed those screws. They're in your face when you try to access the hard drives since I've changed the drives a few times.

Second part was because I had the G5 cover removed, the flimsy metal panel below the graphics card never quite had the same support, so drone was building up through that from the radiator fans. So it would appear... Fitted some one sided sticky acoustic foam to the curved lips of the cover between the metal that you don't see.

Then the other part with the radiator fans since it grooves into that lip to hold itself. As with that cover originally out, the build up was happening when it was all idle. Fitted thick foam to the bottom of the fan cradle as there was a gap between that and top bit of the floor of the case. Which ended up going through that whole metal panel.

With the latch closed with no foam behind it, finally no drone build up. Lovely sleep because of it.