There was also a 30-second "titter" track in the loop, which consisted of individual people laughing quietly. This "titter" track was used to quiet down a laugh and was always playing in the background. When Douglass inserted a hearty laugh, he increased the volume of the titter track to smooth out the final mix. This titter track was expanded to 45 seconds in 1967, later to 60 seconds in 1970, and received overhauls in 1964, 1967 and 1970. Douglass kept recordings fresh, making minor changes every few months, believing that the viewing audience evolved over time. Douglass also had an array of audience clapping, "oohs" and "ahhhs," as well as people moving in their seats (which many producers insisted be constantly audible).