Re:Triangulation to locate sources? (Score 1)

In the mid sixties early seventies, I had a strange interview was interviewing for a position a an electronic technician, and during the interview the interviewers phone rings and he starts a conversation about a theory that states that sound waves exists forever. He then continues with the idea that sensitive equipment could be build that would recover these signals. All of a sudden he states that I was in the room, and this conversation was getting into secure areas. Afterword he dismissed me and I never heard from him again. All along I realized that their was some kind of BS going on, but I could never figure out why he was playing such a game with me.