At what age does it stop being acceptable to be smashing a ball against a wall on a quiet Sunday morning in a residential area?

For 5 minutes? Honestly the OP just sounds moany

If he doesn't go out and doesn't seem to do anything other than practice tennis, What's he going to do if he can no longer practice?

No idea, depends what he decides to do. Might just be a lad who’s never thought to be considerate of his neighbours, or a brat who’d just keep on bashing the ball. Hopefully the former, at age 19 though.

You're not making much sense. He isn't playing tennis with other people is he? And although most autistics are sensory avoidant (all my family) I know one autistic boy who is sensory seeking and has episodes of throwing himself at walls. This sounds like a similar thing.

I would at least avoid saying anything until he's finished uni. It may not seem like such a big thing to most people but this is obviously a huge part of his life and a way of controlling stress. I would avoid upsetting him at the moment.

If he took his ball to the sports centre he could probably be there all day if he wanted to. He's probably been told not to do it for too long where he is because the neighbours are just as irritated by the noise as OP is.

Then what..?

Go to the local sports centre... for 5 minutes? Seriously?

I think I’d go out there right now and tell him if he hits that ball off the fucking wall one more time ….!

I'd say age is relevant because a child under 16 might be expected to be playing in their own garden, whereas over that age they could go to the local sports centre or park alone without needing a parent to supervise whenever they felt the need to smash the ball.

I'd have a quiet word with his parents, OP. They might not realise how loud it sounds over your side.

You are a misery

For 5-10 minutes a time, age is irrelevant. It isn't unacceptable unless of course it was in the middle of the night.

He probably has absolutely no idea the noise is a problem. There are some noises are that universally considered annoying like a child screaming or shouting (and yet lots of parents want to normalise that for the sake of kids having fun). Many people who play sports are so used to the sound of balls hitting and may not even hear that anything. Some people may like the sound of a tennis or basketball because it reminds them of their youth.

Tbh it's a pretty far reach to imply this boy has special needs. He sounds like a perfectly normal boy who got into tennis, spent his teens playing and practices for 10mins daily in his own garden. Autistic boys also rarely get into tennis which is a very social sport and requires constant interactions with other people like trainers, opponents, teammates etc. Even casual games involve a lot of small talk while playing so it's the last sport ASD boys would enjoy.

what age does it stop being acceptable. As an adult you have more awareness of how your actions affect others.

I would guess that would depend on whether or not he does have special needs and, if so, how severe they are.

You've said both that he doesn't seem to go out and that you see him walking alone around the village a lot, so which is it, and what's. your assessment?

I personally don't think 10 minute sessions are unreasonable, but if you do, why not mention that pleasantly to the parents and see what they say?

Duration changes everything. It's ten minutes. That's not a problem at all.

Ball games, any ball games should be prohibited in built up areas. As soon as there’s a bit of sun: thump thump on concrete. Whack whack whack up a fence. I’ll be called a misery but it’s anti social.

It’s in daytime hours and only 10 minutes or so at a time? Yes. You are being unreasonable if you ask him to stop.

So at maximum an hour away day at regular intervals?
I don't really see the issue now

Totally agree that regular loud parties would be unacceptable but I think a one-off loud party, when neighbours are given advance warning, is actually easier to cope with than being on the other side of a loud repetitive noise for hours every day. It’s really very intrusive if you have experienced it because you don’t know when it’s going to start or stop and the noise is loud enough to disturb calls but you know that when it does start, it’s going to carry on for ages!

Poor boy

Poor adult man?

He is practising a sport in his own garden in the daytime.

If he was practising the drums in his own garden in the daytime, would that be acceptable?

Yes, having loud parties would be unacceptable because they are a) loud and b) late. This is neither. It's annoying but it's within perfectly acceptable reasonable enjoyment of his own garden.

Yeah I think this as well

once he has somewhere else or something else he would rather be doing

your houses sound quite close

in our present world people make more noise at home because they are just home more - various reasons

upgrade office window to triple glazed sound proof?

It sounds like it could be a way to manage stress if it increased around exam time. I'd leave him to it. If you could manage when your own DC was making noise, you can manage now.