The reality is that the snakes prefer to run than fight, particularly when faced with a physically large threat (cows, horses, man). This is why noise works.... they realize something bigger than them is approaching and they seek to retreat.
Have you ever encountered the water moccasin? They will come after you, they are very aggressive.
As for a running chain saw scaring snakes off...not so sure, encountered the guy below just yesterday when holding a running chain saw, just 6 ft away. He had two buddies I also spotted after taking this pic. I think they are water snakes so they were allowed to live. They went back under some rocks, near my pond, after I kept getting closer wanting better pics.