Neighbor’s dog 😤

So I need advice on how to go about this. I hate to be that kind of neighbor but for months my neighbors dog has been barking incessantly all through the day and night. I’ve hold my tongue all this time because I’m like, you can’t tell a dog not to bark but I’m at my wits end. Since they got the dog I haven’t been able to get a good nights sleep and I’m not the only one that thinks the dog is a nuisance...... I suspect the dog is lonely because the dog is alone in a fenced in yard all day everyday and I’ve never seen them take it out for walks or anything. Should I say something to them about it ? I know people can get defensive when it comes to their pets and I don’t want it to be a problem but idc at this point. Even if they just put it inside during the night or something? Idk. What should I do?