I have a couple of dogs, as soon as I hear them bark they come in or I go out, and it's sorted. They rarely bark just if a fire engine or another dog goes past a 6ft fence we have. But as the dog is left alone it's just anxious. Is it friendly, ? If the owner is unprepared to sort it why don't you have a go, a well aimed squirt from a water pistol or hose every time will do the trick, will take time, but eventually should calm down, and if you also be nice when it's quite treats etc.
It's difficult to complain about a neighbour, I'm lucky our neighbour loves our dogs and often comes round just to take the, out or play . (there huge). There is a happy dog a few gardens down, but I always take things like babies on trains, lawn mowers planes dogs etc as part of life, noise done on purpose to annoy like car steros out side the house winds me up. I do have one side of the garden with a high thick wall, doesn't make a diffence, maybe with some softer stuff like wall or fence and trees hedge it will absorbs the noise better