My Elegoo Neptune 4 Pro was creating too much vibration on the table and even on the ground when printing at high speeds, so I decided to print a simple damper to absorb most of the vibration. The result is a simple parallelepiped created on Autodesk Fusion. 

The size is 7 x 5 x 3 centimeters, but you can adjust to your needs. Less than 3 centimeters in height will absorb less vibration and more than 5 maybe is just overkill or worse, can become wobbly.

The trick is to print in TPU, 15% infill gyroid, 4 layers at base and top, 2 walls. I printed with 0.2mm layer on a 0.4mm extruder.

After printing four and putting under the stock leg, the noise was drastically reduced. Mostly of the noise was being generated by the printer's vibration, like a hand crank music box.

Simple idea required a simple design and it works.