So this is just an idea at the moment.
I have a 30' x 30' two story external garage. The ground floor is my dedicated workshop area. The second floor is insulated and sheet rocked but is just used for storage. Both floors have 10'+ high ceilings.
I have a 1.5HP single stage Jet DC that I have converted into a two stage that currently resides on the ground floor. This works fine with all my current tools. The first stage bin is a 55 gallon metal drum.
It seems most of the noise comes out of DC via the filter. So as you can see, my ducting plumbing is not optimal, but it seems to work, but I'm thinking about relocating the filter and lower bag up to the second floor, with the possibility of making a splitter that would allow me to direct vent outside or through the filter depending upon time of year. In winter, if I'm heating, I would vent through the filter to minimize having to bring cold air into the garage.
I want to keep the 55 gallon drum on the ground floor for ease of emptying and keeping an eye on the chute into the bin, clogging, when I'm dumping a lot of chips during an operation, mostly planing wide boards on my A3-31.
I have a CNC arriving in the next couple of months, and so, I plan on running the DC a lot more on a continuous basis, so I'd like to mitigate as much noise as possible, which is the reason for the idea of relocating the filter. I don't really have enough space on the ground floor to build a dedicated closet for the DC.
At some point, I plan to upgrade my system to something like a CV1800, at which point I'll mostly redo all my duct work.