A rotary rock tumbler, such as a Lortone or Thumler, should be much quieter than any vibratory tumbler. Most of them have the inside of the drum rubber lined, which also helps them run quieter. They cost a little more than a vibratory tumbler, but are built to be able to run for weeks on end.
Don't get an RCBS Sidewinder; they're a lot more expensive and have lower capacity than a comparable rock tumbler.