Howling or barking? Howling definitely means unhappy in this case. Wolves howl as a means of calling to locate the rest of the pack, and get it together for the evening or to tell other packs where they are. Dogs seem to have got this trait too; mine all howl, for the first reason, of an evening, and sometimes for the second when three are in one pen and suddenly decide to call out for the other six in another (who respond by howling too!).
Lonely dogs bark the 'lonely bark',a sole bark at regular, evenly paced, intervals and this may go on for hours. It's quite distinct from other barking.
Howling or lonely barking. this dog's is alone, lonely, and calling out for company. The council can deal with noise nuisance, but really the RSPCA should be called in, to give the owner advice and/or to remove the dog.