Simulation study of vocoder communication in air traffic control

Human factors researchers at the Federal Aviation Administration (FAA) William J. Hughes Technical Center conducted a real time person-in-the-loop evaluation comparing two vocoder systems and traditional analog radio communications. Vocoders digitize and compress speech signals to use less communication spectrum. Active Air Traffic Control Specialists (ATCSs) from FAA Terminal Radar Approach CONtrol (TRACON) facilities worked simulated traffic under moderate and high levels of task load. ATCSs used all three systems over a 1-week period. Results indicated that the controllers performed well when using the two vocoders and the analog communications system. They rated one vocoder as less intelligible and acceptable than the other but preferred analog radio. The more highly rated vocoder was a close second to analog radio in terms of intelligibility. Researchers concluded that vocoders are a potential solution to frequency congestion