A lot of the noise generated while printing is actually being transmitted into the surface the printer is sitting on and from there into the room, the floor and the structure of the house. I have my printer in an upstairs room in my house, and I could even hear it downstairs, transmitted through the floor.

After doing a bunch of research, I happened on a vibration damping material called Sorbothane. We use it at work to damp vibrations in laser systems. It's readily available from Amazon and other sources in a variety of shapes.

I designed some round feet that clip to the bottom of the printer frame, allowing me to mount 3/4" hemispherical Sorbothane feet to the printer. Using six of these feet with the Durometer 70 Sorbothane, the sound is reduced substantially, and it no longer transmits through the walls and floor of my house.

You can download the parts here: http://www.thingiverse.com/thing:322915

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