Creation of unseen triphones from diphones and monophones using a speech production approach

With limited training data, infrequent triphone models for speech recognition are not observed in sufficient numbers. In this paper, a speech production approach is used to predict the characteristics of unseen triphones by concatenating diphones and/or monophones in the parametric representation of a formant speech synthesiser. The parameter trajectories are estimated by interpolation between the endpoints of the original units. The spectral states of the created triphone are generated by the speech synthesiser. Evaluation of the proposed technique has been performed using spectral error measurements and recognition candidate rescoring of N-best lists. In both cases, the created triphones are shown to perform better than the shorter units from which they were constructed.