I think this is a difficult situation and imagine it plays on your mind a lot. If you can't hear yourself talking to them, I think ear plugs are a good idea. Or perhaps you could you sleep in a different room?
In my experience, there are a lot of people who just don't realise how their behaviour affects other people and lack the capacity to reflect or empathise. Perhaps they would respond favourably if you had a gentle word with them? I think it'd be best to talk to the young person directly, rather than through his parents, as he is an adult. May be highlighting the noise problem will have a knock-on effect with his parents.
We had a similar problem with a neighbour's daughter's boyfriend - he used to honk the car's horn (many times) when he came round to pick her up (rude, eh?!). At the time I had a new and fractious baby. At the end of my tether I took him, screaming at the top of his lungs, out to the guy and asked if he'd like to get the baby back to sleep as he'd done such a good job of waking him up. He didn't do it again!
I question whether car doors need to be slammed to shut? Over 40 years of car ownership this hasn't been the case with us!
I hope you get it sorted so you can sleep in peace.
Unite the Kingdom and Pro Palestine marches Cup 16th May 2026



Now that's how to handle a delicate situation ??? 
