Big tools sometimes make big noises and that's OK as long as it's short-duration like the table saw.  The problem is the long-running noisy ones like the dust collector and air compressor.  After living with the noise in my old shop, I decided to put these into their own noise-reducing closet.  Others choose to install them outside the work building, run the necessary piping and electrical through the wall and wrap the tools in a small bump-out.  That wouldn't work well for my building so I decided to keep them inside.

I collected a lot of noise-reducing tips and came up with the following plan:

- build a free-floating platform and wrap it in industrial noise-reducing carpet underlayment
- build non-load bearing walls and use soundboard, instead of drywall, inside and out, installed with RC-1 channel
- loosely place fiberglass batts between the studs
- to get access inside, build an outswinging double-door 2x4 unit and tightly weatherstrip

The front and side walls are just tacked into place.  You can see the carpet padding tacked to the platform - it's free-floating inside the framing.  A pre-hung door system was too expensive for the purpose, so I decided to make my own doors and frame with 2x4s.

I screwed together the door studs for strength then mounted them in the frames on heavy-duty hinges.  Then I began mounting the RC-1 channels - these are metal strips that have a squared-off S shape.  One leg of the S screws into the studs, the middle of the S is about 1/2" offset, then the other leg of the S is used to mount the sound board.  This makes a very light, non-rigid way to mount the soundboard to the studs, greatly decreasing the mechanical noise and vibration transmission.  We'll see how good it does once everything is running.  I'm partway through mounting the soundboard now.  I'll fill the cracks between panels with expanding foam, and put fiberglass batts loosely in the stud bays.

The last step was to put the channel and soundboard on the outside.  I mounted everything with the doors closed, then used my reciprocating saw to cut around the doors.  I then installed a latch and handle.

With fingers crossed, I fired up the dust collector and air compressor and shut the doors.  Wow, what a difference!  Actually better than I was hoping for.  Now I can work and not have to put up with all of that noise.  I'll run the dust collector piping out of the room after the drywall goes on the ceiling.