Understanding and improving speech recognition performance through the use of diagnostic tools

The goal of this work is to highlight aspects of an experiment other than the word error rate. When a speech recognition experiment is performed, the word error rate provides no insight into the factors responsible for the recognition errors. We begin this paper by describing an experiment which contrasts the language of conversational speech with that of text from the Wall Street Journal. The remainder of the paper is devoted to the description of a more general approach to performance diagnosis which identifies significant sources of error in a given experiment. The technique is based on the use of binary classification trees; we refer to the results of our analyses as diagnostic trees. Beyond providing understanding, diagnostic trees allow for improvements in the performance of a recognizer through the use of feedback provided by quantifying confidence in the recognition