I assume there's an audio technician (almost certainly not his/her title) whose job it is to watch the scene(s) with hands on some controls, inserting certain kinds of laughs (chucks, belly laughs, etc) at the right times and of the correct duration and level.
And is this something the director gets involved in.
"More guffaw. That line kills."
@smays “what do you do for a living?”
“I tell people when to laugh”
Once upon a time sitcoms were filmed before a live audience that either laughed legit or laughed when the sign flashed? But it's long been canned. And how did they get authentic laughter to put IN the can? Damned hard to fake laugh. I've got a LOT of questions.
@jerry @smays there is a cool podcast about the machine that generates the sitcom laughs: https://99percentinvisible.org/episode/the-laff-box/