About 2 years out of college, I bought a house. The neighbors on one side of me had a dog that would wait until about 3am, and decide to start barking. The neighbors bedroom was on the other side of the house, and they seemed not to notice it.

The next day I discussed it with them, and got the imfamous, "We don't hear it, so not sure what we can do." So that night, in the wee hours, when he started barking, I knocked on their front door, until the light came on, and they opened the door quite pissed. I explained if I couldn't sleep because of their dog, I'd make sure they knew their dog was keeping me up!

This went on for a couple nights, and then I got a visit from the police telling me that I was disturbing the peace! They said the dog was not their jurisdiction, but to stop waking the neighbors. Dog Control was worthless, as they didn't want to show up in the wee hours, and wouldn't take my word for it.

I like dogs, but at this point I figured it was time for some Pavlovian training. It was February in Michigan, nightly temperature of about 25F. So that evening I pulled the hose out of the garage, hooked it up to the hose bib on that side of the house, put a nozzle on the end, and made sure it dripped slowly so as not to freeze.

About 2:30am the dog starts in again. I went outside, peeked over the fence, and hosed the dog down until he went back in his doghouse. Started walking back toward my house, and the dog started in again... So I hosed him down again, until he went back in his doghouse. He came half way out, and made one half hearted bark, and I hosed him down again. We played this game for about an hour, and I began to hose him down when he even came out of the doghouse. He had to be miserable... eventually I walked back inside, and didn't hear from him again.

I planned to do the same thing the next night, but didn't hear a peep from the dog. That was the last I heard from him at night.

I would have preferred to hose down the neighbors!

So, your idea of a loud high pitch might work. I would suggest that you probably can get away with a frequency of 20KHz or so, as most peoples hearing becomes very directional above 14-15KHz, and it will likely not be an issue, and probably no one but the dogs will hear it. At adequate SPL levels, that will be pushing some good power into a tweeter. Better get yourself a good brand or you'll blow it pretty quickly with a solid tone. Some of the Electro-Voice horn tweeters I've seen would stand up to that sort of punishment.