JJ is describing a conversation with her husband that her son overheard. She mentions that they need a cone of silence in the house. The cone of silence was a running gag in the series Get Smart. Maxwell Smart, Agent 86, a secret agent working for CONTROL, would insist that the Chief activate the cone when having top secret conversations. A clear dome would drop from the ceiling to surround them and prevent eavesdropping. The joke was that they couldn't even hear each other.