3D prints can take a long time, leading many to print overnight. But if you've got one in your house, the noise may keep you or family members up; if you live in an apartment, even worse, you may keep the neighbors up.
Stefan over at CNC Kitchen has a fix, developed after literally losing sleep over the din of his printer: "I started putting cheap pavers below my machines that you can get in many different sizes from the hardware store."
Add some foam blocks beneath to protect your tabletop, make sure you don't have any wires rubbing the concrete, and you're good to go. The vast majority of the sound is eliminated.
That's the whole tip, but if you need convincing, or just want to see more data, Stefan has fastidiously measured the sound difference before/after in the video below. He also explains why the chunk of concrete works better than other noise-reduction solution in great detail: