[Seric]

We have the same issue with some renters who live behind us. We have left an anonymous note and even contacted their landlord. The response to their landlord was incredibly rude and almost belligerent, demanding to know who made the complaint. If I were going to go to their doorstep, I'd have to take half the neighborhood with me in case they tried to physically harm me. Whatever you do, do NOT talk to them when you are angry, that will usually lead to bad results.

If you feel comfortable talking with the neighbor, give it a shot. Consistent reminders that their dog is a nuisance could eventually solve the issue. If not getting your local authorities involved can send the message. If you live in an area with a Home Owners Association, that may be helpful since most have an ordinance against excessive barking.