Brian Brady 
It’s probably the biggest cause of neighbour disputes – barking dogs. While the owner is away, their dog can get up to all sorts of things, least of which is incessant barking, causing strain on your neighbourly relationships.
How do you approach a neighbour that has a barking dog that they don’t know about?
If you know them:
1) Pop over when you see their car in the driveway and mention to them that while they’ve been out, their dog has been barking quite often and you thought they should know.
2) If you have done the first step and things haven’t improved, pop over again and let your neighbour know that the dog barking has become rather bad of late and that you think something might need to be done so the neighbourhood doesn’t get cranky about it.
3) Ask other neighbours if they’re feeling the same way as you about the dog barking, and see if they can approach your neighbour as well. Having multiple people raise the issue may increase its importance with the dog owner.
4) You can contact your local Council, but this should be almost a last resort as it can cause friction between you and your neighbour if they feel that you’re being unreasonable (whether you think you are or not).
If you don’t know them:
1) If you’re not comfortable knocking on the door, write a note and pop it in your neighbour’s letterbox. Put your name and house number on it, and word it politely so that they can approach you for further information or talk to you about it at a later date – they may want to find out from you if the problem is fixed or not, so they’ll need to know who to ask.
2) If you know other neighbours, you can do the same as in step 3 above.
3) Drop another note in the dog owner’s letterbox, and maybe look up and suggest some local dog obedience classes. Word your letting as a concerned animal lover – show you’re empathetic and are trying to help with possible solutions rather than just simply complain.
4) As a last resort, contact your local Council for further advice on handling the dog barking situation.
Some dogs take time to settle in, get to know their surroundings, or just simply need more attention. If you always keep the dog’s best interest in mind, you should find that the problem can be solved by helping the owner realise that there is a problem that they need to fix.