VOCODER EVALUATION STUDIES.
Scientific rept. no. 3,
RADIO CORP OF AMERICA CAMDEN N J DEFENSE ELECTRONIC PRODUCTS
Pagination or Media Count:
Speech transmitted via vocoder suffers peculiar distortions which make evaluation difficult. Three terms often used to describe the performance of a vocoder are intelligibility, speech quality, and talker recognition. The problem of defining these terms is discussed. Intelligibility and talker recognition are susceptible of quantitative comparisons but no technique for measurement on an absolute scale is known. A survey was made of approximately 70 Air Force communications personnel to elicit their judgments of six speech samples representing a range of vocoder systems. Listeners were asked for judgments regarding intelligibility, speech quality, and talker recognition, as well as suitability for normal use and preference. The results will serve as a guide in the development of improved vocoder systems. Laboratory measurements were made of intelligibility and talker recognition for the condition represented in the survey and for additional vocoder modifications, including the effects of one, two and three-bit quantization of the normalized spectrum. Author