Noise adaptive spoken dialog system based on selection of multiple dialog strategies

Speech recognition under noisy environment is one of the hottest topic in the speech recognition research. In this paper, we propose a method to improve accuracy of spoken dialog system from a dialog strategy point of view. In the proposed method, the dialog system automatically changes its dialog strategy according to the estimated recognition accuracy in noisy environment in order to keep the performance of the system constant. In a noisy environment, the system restricts its grammar and vocabulary to improve recognition accuracy. On the other hand, the system accepts any utterance from a user in a noise-free environment. To realize this strategy, we investigated a method to avoid user's out-of-grammar utterances through an instruction given by the system to a user. Furthermore, we developed a method to estimate recognition accuracy from features extracted from noise signal. Finally, we constructed a proposed dialog system and confirmed its effectiveness.