PRUSA I3 POWER SUPPLY MUFFLER.

thingiverse

I own two of these printers and they are situated in my bedroom. Most of my prints take more than three or four hours to complete, and they happen at night. The fans on the two printers can be quite loud because they are facing right at me as they sit on a desk at the foot of my bed. I noticed that someone else had done something similar on this forum, but it was for another type of power supply. So, I used sound canceling technology to build this project. As you can see in the photos, I used foam to help absorb some sound as it exits. You could use a similar material, such as fiberglass, which works well too. I've tested this and measured the sound with a sound meter, and it works very effectively at reducing noise by about 85%. This design does not restrict airflow, which would be bad.