A commercial large-vocabulary discrete speech recognition system: DragonDictate

DragonDictate is currently the only commercially available general-purpose, large-vocabulary speech recognition system. It uses discrete speech and is speaker-dependent, adapting to the speaker's voice and language model with every word. Its acoustic adaptability is based in a three-level phonology and a stochastic model of production. The phonological levels are phonemes, augmented triphones (phonemes-in-context or PICs), and steady-state spectral slices that are concatenated to approximate the spectra of these PICs (phonetic elements or PELs) and thus of words. Production is treated as a hidden Markov process, which the recognizer has to identify from its output, the spoken word. Findings of practical value to speech recognition are presented from research on six European languages.