Improving Children's Speech Recognition by HMM Interpolation with an Adults' Speech Recognizer

In this paper we address the problem of building a good speech recognizer if there is only a small amount of training data available. The acoustic models can be improved by interpolation with the well-trained models of a second recognizer from a different application scenario. In our case, we interpolate a children’s speech recognizer with a recognizer for adults’ speech. Each hidden Markov model has its own set of interpolation partners; experiments were conducted with up to 50 partners. The interpolation weights are estimated automatically on a validation set using the EM algorithm. The word accuracy of the children’s speech recognizer could be improved from 74.6% to 81.5%. This is a relative improvement of almost 10%.