Loud: chop saw, cheap air compressors, air tools, import angle
grinders.
Quiet: bandsaw, old piston air compressor with input filter & belted to
run slower, some electric grinders.

Metal chips tend to stick to rubber-soled shoes and rugs.

I do all my welding and a lot of my louder, messier metalworking out in
the driveway. My biker/truck driver/construction worker neighbors
haven't complained yet.

Jim W