The solution
It was decided that the most effective way of reducing the amount of vibratory energy reaching the external radiating surface of the machine would be to reduce the response of the structure at the point of impact, ie at the bean tray itself.
This was achieved by applying point-fixed damping to the tray in the form of 2 mm thick steel plate, plug-welded to the underside of the bean tray between its existing tubular steel stiffeners. Acoustic resonance in the void beneath the tray was reduced by filling it with 96 to 128 kg/m3mineral wool slab.