Training of stream weights for the decoding of speech using parallel feature streams

In speech recognition systems, information from multiple sources such as different feature streams can be combined in many different ways to yield better recognition accuracy. In general , information may be combined at the level of the incoming feature vectors, at the level of the decoding process, or after hypothesis generation. In this paper we focus on the specific case where parallel streams of features are used simultaneously during search to generate a hypothesis, or a set of hypotheses. In this case the contributions of the individual features to the score associated with a frame of speech must be weighted appropriately during search. In this paper we present an offline data-driven algorithm for determining the weights to be associated with each feature stream for combining acoustic likelihoods for each frame. Experimental results show that the word error rates (WERs) obtained using the proposed algorithm are lower than those obtained using conventional schemes for parallel feature combination.