Human factors evaluation of vocoders for air traffic control (ATC) environments phase II

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Authors: Brian Carver
Annmarie Heinze
James L. LaDue
Randy Sollenberger, PhD.

Sollenberger, R. L., La Due, J. L., Carver, B., & Heinze, A. (1997). Human factors evaluation of vocoders for air traffic control (ATC) environments phase II: ATC Simulation (DOT/FAA/CT-TN97/25). Atlantic City International Airport: Federal Aviation Administration William J. Hughes Technical Center.


Vocoders offer a potential solution to radio congestion by digitizing human speech and compressing the signal to achieve low bandwidth voice transmissions. A reduction in bandwidth will allow the addition of more communication channels to the system and reduce radio congestion. This air traffic control simulation study is the second phase of a research effort to compare the effectiveness of two 4.8 kbps vocoders (designated as A and B for test purposes) with the current analog radio communication system. Sixteen air traffic controllers from Level 5 Terminal Radar Approach Controls participated in the study and performed 12 one-hour traffic scenarios over 3 days of testing. Scenarios consisted of medium and high traffic volumes designed to produce different levels of controller taskload. The communications configuration allowed each simulation pilot to transmit with jet, propeller, or helicopter background noises. The results indicated that the vocoders did not affect controller workload or performance. In general, intelligibility and acceptability ratings were highest for analog radio, slightly lower for vocoder B, and lowest for vocoder A. In addition, intelligibility and acceptability ratings were highest for jet background noise, slightly lower for propeller background noise, and lowest for helicopter background noise. Controller taskload had no effect on intelligibility and acceptability. This human factors evaluation indicated that both vocoders were highly intelligible and acceptable for air traffic control environments. Even the least preferred vocoder did not substantially interfere with controller performance. This study suggests that vocoder technology could replace the current analog radio system in the future.

Updated: May 04, 2012 11:21 AM