Originally Posted By AeroE:
A rotary tumbler is quiet. One that shakes can't be quiet, so what we do is set them on a pad to dampen transmission of the sound to whatever the machine is sitting on. Don't block the air vents.
Midway has their vibratory tumbler on sale right now.
Just remember that sitting it on a pad, a pad that is noticeably cushioning it from the support surface, can partially negate the operation of the tumbler and make it less effective. So it could end up taking longer to clean the brass if this cushioning is effective. I.E., there is a direct inverse relationship between buffering and effectiveness. While it might not be linear or directly proportional, it still exists.
Mine run on the concrete floor of my garage. That's far enough away that the sound doesn't affect me much. And the environment is still somewhat controlled. Gets kind of hot out there in the summer, but it's still pretty good.
I have the standard size Hornady tumbler and it's not too bad. I also have the big-ass Dillon tumbler. I load it up pretty well and it's noisy as hell.
Probably the best thing you can do is to run a full corn cob media load, and only load the tumbler to about half the specified capacity of brass. That will minimize the metal contact with the plastic tub, while still allowing the media to properly clean it. And cushion the associated noise as well.