is there away to limit enemys hearing abilty like making them hear between 0.1 to infinity but sounds like 0.01 they cant hear???
You can allow an actor to sense pawns in the game world by assigning them the following component : https://docs.unrealengine.com/latest/INT/API/Runtime/AIModule/Perception/UPawnSensingComponent/index.html
It looks like that component exposes a function called - CanHear - which I assume is called when a noise needs to be evaluated to determine whether or not the pawn can hear it. I assume somewhere in there you could adjust the limits / range of what auditory frequencies could be heard.
I don’t have a shorter / more concise answer for you but I’m guessing here that it is possible. If you want more information / an example of UPawnSensingComponent being used, I suggest you check out Tom Looman’s survival game sample as I’m pretty sure he uses this component on his zombies to detect the player.