While those work for many, the frequencies are just above the upper range of human hearing normally and that means they can cause several bad reactions in humans.
Headaches, epileptic seizure, and a few other symptomatic reactions can occur.
I can not use sonic generators because of sensitivity in both my wife and myself. Plus we have three
LGD's that would not appreciate the use of those.
Fences might not be a feasible solution for you, in which case a subsonic frequency generator might work better in your situation
should you find you have recurring symptomatic reactions.
Redhawk