A week of research, finding out yet more information about my planned welding setup.
Friday I was in Brisbane, visiting machinery shops, and looking at industrial equipment. So far, I’ve checked out a “silent” air compressor, which isn’t any louder than an air conditioner’s outdoor component, and a metal-cutting bandsaw, which likewise is very quiet. Both of them are quiet enough to talk over, as opposed to normal compressors, or metal cold saws / abrasive saws, which require hearing protection to avoid permanent damage.
All in all, good ideas for equipment intended to be used in a residential area.