canned laughter n.,
informal The sounds of laughter heard on certain television programs that were obviously not recorded in front of a live audience and are played for the benefit of the audience from a stereo track to underscore the funny points.
"How can there be an audience in this show when it is taking place in the jungle?
■ Why, it's canned laughter you're hearing." [TahlilGaran] English Idioms Dictionary ▲