I am sure there is some law which states that you are entitled to 'go about your own peaceful and merry way without undue interference from others', or something similar, which this should fall under.
We had similar issues with a neighbour and only found this out when things boiled over and the police became involved. Previously they had not wanted to know when we reported that we were having issues, so you may need to push it with them to get a response.
Neighbour issues have become more far prevalent. so most forces now have someone who is specifically trained to deal with that sort of thing. I am talking about England in my case, so am not sure if the laws are the same in Scotland.