16yo ds disappears into his bedroom and his sound-cancelling headphones for hours at a time at every opportunity.
In our house the 'cook' calls for everyone to come and eat, and you're expected to stop what you're doing and come to the table. We might give a 5min warning, or call people a bit earlier than necessary so that they can clear/lay the table.
Ds obviously cannot hear us call.
He knows that we generally start eating some time between 6.30 and 7.00, and has agreed to come down and find out around that time. If he doesn't, AIBU not to go upstairs and talk to him directly, but to just go ahead with the meal without him?