I tried six of these out in an effort to protect some of my turf that was getting dead spots due to dog and cat waste, and met with limited success. Most cats stayed away from the courtyard where I placed them, as long as the batteries held out. When the batteries went, the cats were back within a day or two. Dogs did not seem to be as bothered by the sounds emitted by the device. A few did the doggy version of a flinch when the device activated, but few were deterred, and none of the ones on leashes were bothered enough to ask their human to go elsewhere. I know it's call a "Cat Repellent", but I've never met anyone whose real problem was cats. Some people reported being able to hear the "ultrasonic" sound, and I've got to believe them because most didn't ever notice the unit, but no one was bother beyond wondering where it was coming from. If you have an actual cat problem, especially in an area with limited access, I would recommend givving this a try, but I'm won't recommend trying to cover a blanket area. The cost per area of coverage is to high.