My modded 1377 is louder than silent, but not as loud as a ruger 10/22. Mine has a 14 inch barrel with power mods and a factory Crosman muzzlebrake. In the basement, it makes quite a little noise, which gets a bit louder with every pump. Out back, not so bad...My neighbors don't care, but I live in a small country town in Ohio.
Another noise thing that I don't really like is the slap of the pump when closing the handle pumping it up - so I stuck some felt to the bottom of the pump tube and the inside of the pump handle, and it is a LOT more quiet.