Well I am not sure what stainless media is... I use just good ol' walnut media that you can get in bulk at either a pet supply store (for Lizard bedding) or Harbor Freight. Corn cob media for the final step.
The tumbler is a Lortone QT12 which is a 12 lbs. unit and is the biggest they make. They are not cheap new ( kind of a pro-am model) before making the final step to a professional tumbler. You can find them on eBay for an acceptable price. The nice thing about Lortone is you can buy all the parts for them (minus the frame) to them going for a long time!
They're quiet because they're belt/pulley driven instead of gear driven. The tub is made of a solid rubber with a lid that seal tight so it contains the noise of the media and brass very well. My wife never says a word about when I use it (in the basement), and I forget about it if I don't set a reminder on my phone. When I use the vibratory cleaner... you can't forget unless you can't hear.
This should explain the stainless media.
https://www.indianagunowners.com/fo...tainless_steel_polishing_media_for_brass.html