I have a tourquoise Blue thing called a "Pet-Agree"
its an ultrasonic sound maker
its VERY loud to a Dog, not to us, and it is directional
point it off to the side, its a lot less loud to the animal (I use it on my Mothers Dog, she is taught to come if its not loud, and to back off if it IS loud
but she does back off even from a full out running AT me (I know, I dislike untrained animals as well, but she is getting a LOT better)