CVSD Intelligibility Testing

A key performance characteristic of a voice radio is the intelligibility of the delivered speech under all pertinent operating conditions. The creation of special procedures and the application of formal experimental design methods are required to adequately evaluate the intelligibility performance for advanced radio designs, such as the JTIDS and Enhanced JTIDS (EJS) radios, due to the number of independent variables and interactions of variables that affect performance, particularly where operating conditions involve jammers and the reception of simultaneous voice messages. For an investigation of the voice intelligibility of 16 kilobit per second Continuously Variable Slope Delta (CVSD) modulation, this paper describes an approach which relates the results of the Diagnostic Rhyme Test (DRT) to a variety of test factors (e.g., the bit-error-rate) using the statistical techniques of regression analysis to express the relationships obtained and analyze their validity. The test and evaluation procedures, the results obtained, and the models developed to characterize the DRT intelligibility are presented.