The effort to disable electronics has remained mostly secret. But in 2001, the Air Force publicly announced that it had made substantial progress in developing microwave weapons that target people, when it unveiled the Active Denial System.
Development of the system began in the 1990s with the Air Force's efforts to explore the biological effects of microwaves. A project code-named Hello studied how to modulate the clicking or buzzing sounds produced by microwave heating in the inner ear, to produce psychologically devastating 'voices in the head'. 'Goodbye' explored the use of microwaves for crowd control. And 'Good Night' looked at whether they could be used to kill people.












