Robust Real-Time Face Detection
International Journal of Computer Vision
Two-channel-based Noise Reduction in a Complex Spectrum Plane for Hands-free Communication System
Journal of VLSI Signal Processing Systems
An iterative image registration technique with an application to stereo vision
IJCAI'81 Proceedings of the 7th international joint conference on Artificial intelligence - Volume 2
Blind separation of speech mixtures via time-frequency masking
IEEE Transactions on Signal Processing
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A new noise reduction method suitable for autonomous mobile robots was proposed and applied to pre-processing of a hands-free spoken dialogue system. When a robot talks with a conversational partner in real environments, not only speech utterances by the partner but also various types of noise, such as directional noise, diffuse noise, and noise from the robot, are observed at microphones. We attempted to remove these types of noise simultaneously with small and light-weighted devices and low-computational-cost algorithms. We assumed that the conversational partner of the robot was in front of the robot. In this case, the aim of the proposed method is extracting speech signals coming from the frontal direction of the robot. The proposed noise reduction system was evaluated in the presence of various types of noise: the number of word errors was reduced by 69% as compared to the conventional methods. The proposed robot auditory system can also cope with the case in which a conversational partner (i.e., a sound source) moves from the front of the robot: the sound source was localized by face detection and tracking using facial images obtained from a camera mounted on an eye of the robot. As a result, various types of noise could be reduced in real time, irrespective of the sound source positions, by combining speech information with image information.