Multilingual subjective methodology and evaluation of low-rate digital voice processors

The methodology and results for a multilingual evaluation of source encoding algorithms operating at 16 kbit/s are presented. The evaluation was conducted in three languages (English, French, and Madarin), using listener opinion subjective assessments to determine whether 'toll-quality' performance is possible at 16 kbit/s. The study demonstrated that toll-quality voice is indeed possible at 16 kbit/s, and that several of the methods evaluated are more robust under high bit error conditions than either 32- or 64-kbit/s encoding. Thus, 16-kbit/s voice coding technology is currently suitable for many applications with the public-switched telephone network, including the next generation of digital circuit multiplication equipment, and integrated services digital network videotelephony.