Hook up a xenon strobe to a sound switch, at 15 feet it should be blinding. If the sensitivity is low enough for just nearby barking, should be alright. If the dog can't see, he won't advertise his presence. Plus it will alert your deaf neighbor that his dogs are barking. If the neighbor is just too lazy to properly train his animals, then he might mistake the strobe for a camera flash, and believe somebody is preparing to cause him some legal problems, which you will eventual find to be the most effective and sane route...