Alot of good info here of deer reaction.
How alert the deer are, etc.
I believe, deer are more sensitive to noises that are in close proximity to them. An alert deer won't do more than look towards the sorce of a rifle shot from 1000 yards away, but jump out of their skin if they hear a twig snap at 60 yards. We need to be in close proximity to take deer with our equipment, so the quieter it can be the better. Also the pitch I believe matters. A wouldn't think a lower pitch noise would necessarily sound as threatening as a higher pitched sound.