Microphone array driven speech recognition:: Influence of localization on the word error rate

Interest within the automatic speech recognition (ASR) research community has recently focused on the recognition of speech captured with one or more microphones located in the far field, rather than being mounted on a headset and positioned next to the speaker's mouth. Far field ASR is a natural application for beam forming techniques using an array of microphones. A prerequisite for applying such techniques, however, is a reliable means of speaker localization. In this work, we compare the accuracy of source localization systems based on only audio features, only video features, as well as a combination of audio and video features using speech data collected during seminars held by actual speakers. We also investigate the influence of source localization accuracy on the word error rate (WER) of a far field ASR system, comparing the WERs obtained with position estimates from several automatic source localizers with those obtained from true speaker positions. Our results reveal that accurate speaker localization is crucial for minimizing the error rate of a far field ASR system.