Could you ask him if there's games he plays that are quieter? Or would he be able to tell him friends that he can't say much?
However knowing what (my also normally quiet) ds is like when gaming with friends, then I do have a certain sympathy with both him not wanting to and potential flatmates - especially if walls are thin as they often are in student accommodation.
With ds it varies between the games where it is a constant:
"... Haz, Haz Haz, turn left! I said Left!... AAGGGHH move it... Computer's lagging. Mark don't go there. MOVE!!..." all at top volume followed by a frustrating/delighted bang on the desk.
Or the ones where it's general chat until urgent when the house will be rocked with a sudden "AAGGGH" or "YES!" which normally seems to happen when I'm just dosing off to sleep and I jump a mile!
And when he gets on, he'll often go until midnight. His room is next to ours and there have been times when I've sent him a message telling him to keep it down. He does quieten down, but will forget when things are getting exciting.
I think the headphones make it worse as he doesn't realise how loud he's getting.
It changes him from this quiet, gently speaking 18yo into loud and disturbing for everyone around. I can hear him all over the house when it's particularly exciting.
I don't know what the solution is really. I've been thinking the same with ds, although his bedroom is quite well insulated and a little bit out of the way so shouldn't disturb too many people.
Could you suggest he say does Saturday night, and puts a curfew on it. Or asks the people near to text him if he's disturbing them? Texting is easier than coming round for both.