(FORTUNE Magazine) – Since canned laughter made its first appearance (in 1950's long-forgotten Hank McCune Show), it has become as familiar a part of the television landscape as the NBC peacock or Marv Albert's toupee. But whose chuckles are we actually listening to?

While much of the canned laughter is recycled from recent tapings of shows, some of those chuckles may have been around longer than Morley Safer's ties. Ron Simon, TV curator at the Museum of Television and Radio, says that a few of those cackles, guffaws, and snorts are recorded from golden oldies like I Love Lucy and The Red Skelton Show. Those programs often relied on sight gags, which meant there were no lines of dialogue to muddy the studio audience's laughter.

Today those antiquated laughs show up everywhere--even in shows that are "filmed before a live studio audience," which are often sweetened with extra giggles before airing. Hollywood sound engineers input the tracks into a laugh box, a console that is played like a keyboard to draw forth the appropriate mix of prerecorded sounds. Sure, it's creepy, but it would be more disturbing if people actually had been laughing that hard at Three's Company.

--Reed Tucker