Yup, he does live next door. I suppose i should have said the history.
Before the urchin came along my besty mate, Clare, lived here for a while. We were both out at work in the day, so my brother would pop round and feed the dogs. The dogs are housed in kennels, some 200ft from the house and when my bro was walking back down the path he happened to look up and saw a red light in next doors window. It was a video camera. He had been filming me and Clare sunbathing in the back garden.
It was pointing down onto the lawn and not up at the kennels. The dogs only began to bark a lot when my other neighbour bought a little westie that yaps, it goes up behind the dogs kennels 'yap yap yap', but that was only 12 months ago when that began.
So, my brother goes round there all leary calling him a pervert, and this guy hid behind his wife! I later negotiated with his wife NOT to go to the police if she didn't either about the loud death threat my brother very publicly shouted! 
Things were smooth until 12 months ago when next door got their westie. It does yap, and it is the kind of bark that goes right through you, but i really get on well with the lady on that side.
My dogs have kind of become desensitised actually but if it starts digging right behind their kennel then yes they will bark. I started noticing big chunks of housebrick outside their kennel runs, and lots of mud. I suspected it was my neighbour, but wasn't really sure until Hayleigh (westie owner) called the police because she had been hit in the back with one of these missiles. He had thrown it that hard it had gone over my garden and hit Hayleigh in her own garden. Yes it was the old codger!
There has been no trouble since then. He does still shout when they bark but that just makes all of them, (westie inc) bark more. The westie is tucked up in bed with a little bow by about ten oclock so there is never a peep all through the night.
The thing about him ignoring the urchin is awkward. I had let the hedge grow quite tall between our gardens but he has chopped it right down. So now the urchin can see if he is in his garden.
He is just a little boy, and i encourage him to be pleasant to all the neighbours. I don't wish to scold him, or discourage him, especially as he is on the spectrum. He only says 'hello' and sometimes he asks 'what are you doing?' or asks him about the car her drives. He just doesn't acknowledge him at all. Blanks him. I felt sad today because i was upstairs and i heard the urchin ask him if he liked his new bike that he had for his birthday. Hence the post earlier.
I understand some people may not have any skills with children and i hardly expect him to play santa this year, but ffs, why doesn't he just say "I'm busy kid" instead of blanking him.
i agree with richards post. its amazing what loud music can do... if your willing to invest you could even have it on a timer for when you leave the house... got a good stereo put it out one of your windows facing his house and do it real loud. just an hour a day at the same time every day would be great... i could recommend a few artists... if you dont mind the urchin hearing swearing and he is truly an old coot chances are he wont like swearing so i would highly recommend it [if you dont mind the urchin turning out somewhat like myself, my mom let me start swearing freely around her at 14!!!! :O]
otherwise PPK's idea is good... raw trout... i could even probably air mail him a trout "fresh from the pacific"
stink bombs are a good idea too.... toss em in a open window on a hot day.
uuuh.... if his car has an alarm give it a good thunk with something soft and make the alarm go off in the middle of the night.
order pizzas from a pizza places around town [exclude ones you like to order from because you may wind up on there do not serve list]
theres a really nasty one i can think of but i cant remember the materials. lemme look it up EDIT: if you dont feel like ruining his car you can ruin his front porch too.
theres a few ideas.
