Munch refers to the 'cone of silence' which was a prop device on the spy show. It was a plastic shield that descended from the ceiling to provide an environment for conversation free from eavesdropping. The joke was that the cone of silence always malfunctioned, usually moving up and down, forcing the characters to bob up and down in time with its oscillations.
John Munch and Rene Sheppard come to New York to assist in the investigation of a Government worker's murder in a two-part episode that concludes on Sideshow (1999).