Articulatory representation and speech technology

In this paper we demonstrate the feasibility and usefulness of articulation-based approaches in two major areas of speech technology: speech recognition and speech synthesis. Our articulatory recognition model estimates probabilities of categories of manner and place of articulation, which establish the articulatory feature vector. The transformation from the articulatory level to the symbolic level is performed by hidden Markov models or multi-layer perceptions. Evaluations show that the articulatory approach is a good basis for speaker-independent and speaker-adaptive speech recognition. We are now working on a more realistic articulatory model for speech recognition. An algorithm based on an analysis by synthesis model maps the acoustic signal to 10 articulatory parameters which describe the position of the articulators. EMA (electro-magnetic articulograph) measurements recorded at the University of Munich provide good initial estimates of tongue coordinates. In order to improve articulatory speech synthesis we investigated an accurate physical model for the generation of the glottal source with the aid of a numerical simulation. This model takes into account nonlinear vortical flow and its interaction with sound-waves. The simulation results can be used to improve the articulatory synthesis model developed by Ishizaka and Flanagan (1972).