Thanks men!
High pitched sounds are generally not heard much out in nature.
You've never heard crickets, cicadas, squirrels, rabbits, raccoons; birds from chickadees to ducks to hawks and owls; foxes, bobcats, coyotes, panthers/cougar/mountain lions; frogs and toads (especially tree frogs); whitetails, elk, etc?
I've been fortunate to hunt in MS, AL,TN,SC, GA, CO, NM, and Northern Ontario in all sorts of environments and there's always something vocalizing some time or the other, and it's almost always in a high pitch. About the only low pitchs I've heard that I can think of off-hand is a bull frog, a moose grunting, or a bear.
No idea how you can determine a different pitch would cause a different reaction in an animal because every situation is different and you can't test both to compare reactions.
I've blinked at the wrong time while 20+ feet up a tree and spooked deer, and I've seen a deer stand there and watch with interest while two people were carrying on a conversation.
If I've made a mistake in the facts I listed, please point it out so I can correct it. I've made mistakes before, and I'm sure if I live very much longer I'll make more...but if I can be shown the error of my ways, I'll gladly retract the fallacy.