A laugh track, sometimes called canned laughter by critics, is a collection of pre-recorded audience laughs and applause sounds added to television programs during post-production. The main purpose of the track is to trigger a response from home viewers who may not understand all of the intended humor during a taped sitcom. The belief is that laughter creates laughter, so canned laughter supplements natural reactions to a set-up and punchline. Some television producers call this practice sweetening the track.
The first known use of a recorded laugh track is said to be in 1950, when the producers of the Hank McCune Show added canned laughter after the show's taping. Until that time, other radio and television comedies either used a live studio audience or no canned laughter at all. In 1953, a sound engineer named Charley Douglass invented the Laff Box, a small electronic device containing numerous loops of recorded laughter and applause.
It is rumored that Charley Douglass culled almost all of his laugh track material from in-studio recordings of several different comedy shows, including I Love Lucy, The Red Skelton Show and various live performances by mime Marcel Marceau. Douglass needed to record all different styles of laughter and applause without the sound of dialogue, so it's very possible that he recorded several of Red Skelton's silent clown performances. If this is true, then audience reactions on a modern sitcom may have actually been recorded over 50 years earlier.
Criticism of the laugh track reached a fever pitch during the 1970s. Many sitcoms chose to eliminate the practice altogether or mix live audience reactions with the canned laughter. Filming a show in front of a live audience became a badge of honor for a number of sitcoms. Use of a laugh track was viewed as an attempt to mask weak writing or performances. Even shows that still relied on audio sweetening made efforts to cut back on the practice. The problem was that live audiences did not always provide a usable response, especially after a long day of outtakes and retakes.
Today,the same company created by Charley Douglass offers an upgraded digital version of the original Laff Box. Not only are the original laughter and applause tracks still featured, but additional tracks for foreign audiences and children's shows have been added. Most sitcoms produced today are still recorded in front of a live audience, but a more subtle laugh track can be used to bolster inaudible or weak responses. In the audio world, the effective use of audio sweetening is considered more of an art than a science.