Evaluation of Intelligibility Performance of the DoD Standard LPC-10 Narrowband Vocoder Algorithm in an E3A Aircraft Cabin Acoustic Noise Environment

摘要

Noise recordings and measurement data were collected during an operational flight of an E3A aircraft to characterize the acoustic environment of the E3A controllers. These data were used in preparing speech intelligibility and voice quality test recordings under simulated noise conditions as observed in the E3A. These recordings were incorporated into a library of speech test recordings that includes a number of operational acoustic noise environments, for use in tests of digital voice communications processors and systems. The E3A-environment speech test recordings were used to evaluate intelligibility of the DOD linear-predictive (LPC-10) narrowband vocoder under error-free conditions and with simulated 5 percent JTIDS channel errors. The E3A cabin acoustic noise environment was found to cause a significant change in reducing vocoder intelligibility in comparison with a quiet environment. The addition of 5 percent JTIDS channel errors caused an additional significant drop in intelligibility. Speech in an acoustic noise environment that included the background noise in the E3A cabin caused by the jet engines, and speech interference resulting from communications activity at an adjacent controller position in the E3A cabin (one of the acoustic noise conditions observed and recorded during the operational mission) caused significantly greater impairment of vocoder intelligibility than the jet engine background noise alone.