Synthetic phoneme prototypes in a connected-word speech recognition system

A recognition system based on a reference library of synthetic phoneme prototypes is described. The phoneme templates are specified in terms of formant synthesis parameters. The vocabulary and grammar are described in a finite-state network where each node represents a phoneme. A transition between two phonemes in the net is expanded to a number of new nodes using interpolation on the synthesis parameters or at the spectrum level. For each node, a 16-channel filter bank section is computed from the synthesis parameters. Adaptation to each speaker´s individual voice source spectrum is performed during recognition. Auditory forward masking is incorporated. Speaker-independent recognition results are given for male speakers on isolated words and connected digits. Future improvements include coarticulation and reduction rules and speaker adaptation of phoneme parameters. The method could also be used in combination with hidden Markov models to provide reference data in cases not covered by the training material