Someone was looking for something to keep cats away. I happen to run across this. Not spam, I guess it may look like it.
Here is a link that might be useful: cat stop
It was me, or if it wasn't me its something I'm interested in :-) I will have to check it out a little better. I've tried something similar that was supposed to keep bugs and rodents away but it did not work. And you could hear it. I also have to see if its safe for dogs.