oh my gosh that is exactly the same thing my mums house is double brick and you can hear him in the kitchen from upstairs its bad and his been like this for bout 2 yrs now he needs this oxygen thing to help him breath at night due to he is also over weight and apparently it helps him stop... but its expensive and his also stubborn!!

maybe record him while his asleep and show him in the morning or maybe result to show him how bad it is and tell him he has to sleep in a seperate room till he fixes it thats what my mum did and still does lol