Try to create a small soundproof room just for your S9. In that way, noise will be minimized. There are many tutorials in youtube on how to create a soundproof room.
still, even with this homemade soundproof box its about 55DB
Dude, that's about as loud as normal conversation or about the same as a typical AC.
The db scale is logarithmic so 55db is quite a decrease from the 80db they normally are.
http://www.industrialnoisecontrol.com/comparative-noise-examples.htm