Hey Maecrab, sorry about not checking back here earlier, yes I meant having soft sound absorbing things in the room just doing their normal job, ie carpet on the floor, couch for sitting on etc. Of course if you have a spare carpet to hang on the wall, it might be even better.
I had this experience once when I went into a shop that sells poofs, pillows etc with my daughter who used to scream a lot when she was smaller, and noticed that the screaming really didn't bother me very much in there, whereas at home it would drive me up the wall. Since then I've become much more aware of how sound reverberates in rooms, and try to reduce it where I can. It also helps that we have an anechoic chamber at work, and the guy who built it likes explaining all about it. So I can think about how to adapt these techniques into a low-budget, home setting (though I mostly don't get around to it - too busy w/ other stuff). If you have time you could get really creative while spending minimal $$. Maybe also check out DIY how-tos for improving the acoustics in low-budget band rehearsal rooms etc.?
tl;dr: Sounds reflecting off the walls again and again may be an equal or even bigger problem than sounds getting in in the first place; acoustics may be useful to understand (also interesting if you're a geeky type)
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Father of 2 children diagnosed with ASD, and 2 more who have not been evaluated.