Whether or not the cops will do anything about the neighbors dog depends on what is actually going on.
If the dog is just barking constantly then the cops will likely do nothing or be able to do much but they might be able to speak with the neighbors to tell them to keep the dog quiet.
But if your town has no dog barking or noise ordinance then the cops cannot do much if anything at all.
In that case you would need to contact your city or town and speak with the Mayor about the issue and they can usually resolve the issue.
If the dog is an aggressive dog and attacking you or trying to attack you then calling 911 would be a good idea and they should respond if the dog is out of the pen or running lose and trying to attack you or someone else.
If it's just a barking issue contact the town and speak with the mayor and council about the issue and they can then force them to take care of the issue or get rid of the dog.