vibration and resonance

I need to get rid of vibration and resonance in my homemade rack that is to "lively and rings like a bell". I was told to try DYNAMAT on the underside of the shelves. Would cork be the same or better? What is your experience? Thanks
Thanks for the advice. My rack is 24"x24" shelves 4 high with 5/8's threaded rod holding it together. The shelves are 3/4 plywood. It is spiked to the floor and I am seriously considering putting a granite slab on top. I did get a maple shade 2" thick platform for Christmas to place my player on which brings up another question about footers(soft or spikes).
Do you have the rubber washers between the nuts & the shelves like the salamander racks do?
I built a rack from slate and threaded rods. My rack is very heavy but will wobble if the nuts aren't tight. I really crank them to make it rigid.