As we can read on Wikipedia, Tapper is a 1983 arcade game released by Bally Midway. The goal of the game is to serve beer and collect empty mugs and tips. Robert Seddon has linked us to an article on Edge Online, in which they talk about some removed content from the game:
Sometimes good ideas turn bad when you actually hear them. Such was the case with the burps in Tapper. Wanting to take advantage of a brand-new digitising chip from Texas Instruments, Meyer and Morrison thought it would be a good idea to add a burp every time a character finished a drink.
So, to create the source audio, a group from the Tapper team went into a conference room with a bunch of soft drinks, beers and microphones, and just started burping.
Looking back on the misguided notion, Morrison says: “We put it in, and it was disgusting.” The game was so fast and the drinks were being finished so quickly that you heard constant belching. In the end, the duo didn’t bother installing the burps or the TI chip, although Morrison admits that passing by their office during that phase of development was a treat for all within earshot.