For fear of being lynched, I would like to give you the benefit of my experience, so be nice people.
I had a dog that barked, he was rarely left alone, I'm talking 6 days a year, that was probably the problem, he didn't like being left alone because he wasn't use to it, not because he wasn't exercised or happy or loved.
There are a number of gadgets you can get, sprays, collars and educational games that you put treats in. I tried them all and they didn't work, I was verbally abused and told I wasn't an animal lover. It was a stressful situation and people think you just don't care or are not trying to do anything about it.
In the end if I had to leave him, I would either get someone to come and sit with him or take him with me or if that wasn't possible I would put him in a good kennel for the day where he would get walks twice a day.
The last thing I wanted to do was disturb anyone and you shouldn't have to put up with it from someone else's dog but if they are decent people then you should be able to talk to them.
My advice is if you don't feel able to approach them, write a polite note and put it through their door and ask if you can talk about it, tell them how it is affecting your life, don't fall out with people you have to live next to, doesn't make for a happy life.
Btw I had a Yorkie who lived until 16 years old.