Cosmos pure black vibrations and humming noises in Cases Posted May 2, 2010 Having a day off I've removed screws holding hdds cages and removed blank ones also worked with some bitumen mat with some good effect. So for now I'm left with one major problem: top tray. I don't have any idea what to do with it. Temporary I took it off and vibrations went down to reasonable level. I've tried to put a couple of things below it but bitumen mat was too thick and soft things like cloth, paper or other similar stuff didn't have any effect. So one more question then: how to mount top tray to stop it from vibrating?