A good argument for steam.
Modern roller-bearing steam drifting downhill with proper steam or drifting-valve setting can be quieter than an idling diesel-electric, and certainly quieter than a locomotive in dynamic braking.
True. Personal experience, I was in Roanoke back in the 90’s for a Norfolk-Southern steam excursion and Mighty 611 drifted past where we were standing. I was amazed at how quiet it was when it wasn’t working hard.
Just a gentle “woosh-woosh-woosh” as it rolled past.
When UP 4014 was enroute to West Chicago, my daughter-in-law mentioned how quiet it was as it passed through Elmhurst. It’s also hard to be much quieter than a set of MU cars, something I observed quite early with the South Shore.