Operational Acceptability of 2.4 Kbps Speech for Tactical Communications

This paper describes a series of tests aimed at estimating the operational acceptability of 2.4 kbps LPC speech in high acoustic noise, tactical combat environments. F-15 fighter pilots and E3A (AWACS) controllers, operating in their normal acoustic environments, ran simulated combat missions by communicating via a 2.4 kbps test channel. They then "graded" the channel by means of a brief questionnaire. Three LPC algorithms (with DRT scores of 71, 75 and 80%) were used. The results, although not definitive, suggest that purposeful users will accept lower intelligibility than vocoder designers might expect. The results also indicate a need to examine the effect of listeners\´ acoustic noise level on intelligibility scores.