Speech recognizer-based microphone array processing for robust hands-free speech recognition

We present a new array processing algorithm for microphone array speech recognition. Conventionally, the goal of array processing is to take distorted signals captured by the array and generate a cleaner output waveform. However, speech recognition systems operate on a set of features derived from the waveform, rather than the waveform itself. The goal of an array processor used in conjunction with a recognition system is to generate a waveform which produces a set of recognition features which maximize die likelihood for the words that are spoken, rather than to minimize the waveform distortion. We propose a new array processing algorithm which maximizes the likelihood of the recognition features. This is accomplished through the use of a new objective function which utilizes information from the recognition system itself, obtained in an unsupervised manner, to optimize the parameters of a filter-and-sum array processor. Using the proposed method, improvements in word error rate of up to 36% over conventional methods are achieved on real microphone array tasks in a wide range of environments.