I assume the dogs are being left alone and it's not just that the dogs bark while the owner is there listening to them. In that case, the barking is probably out of boredom, and you should probably let the owner klnow that it is happeneing so he or she can take corrective action.
If the owner is around, then the barking likely gets just as annoying to them.
I personally believe that, in general, people need to toughen up and just learn to live with life's little inconveniences like smoke in public, barking dogs perople who cut you off in traffic and the like. As much as you may think others are inconsiderate for letting dogs bark, letting smoke float, etc., I think too many people have come to believe that all things that they personally dislike should be forbidden and take it as a personal slight when they do occur without permission.
I agree with Seneca the Younger who suggested that, if things like that bother you, then you need to work on training yourself to be more tolerant based on the self-realization that things that you dislike can and will occur regularly. If you can't handle that basic truth of life, then in a real sense, you are the one with the problem (at least every bit as much as those who let such things occur). Stated differently, if deep down you secretly believe in a perfect world where dogs never be allowed bark unless their owners consult you and get your prior consent to the noise, you are going to be needlessly unhappy and annoyed.