MULTI-MICROPHONE NOISE REDUCTION TECHNIQUES FOR HANDS-FR EE SPEECH RECOGNITION -A COMPARATIVE STUDY-

In this paper we will describe different multi-microphone noise reduction techniques as for example front-end system s for a command speaker-independent word recognizer in an office environment. Our focus lies on examining the recognition rate if the noise source is not gaussian and stationar y, but a second speaker in the same room. In this case standard noise reduction techniques like spectral subtraction will fail, and only multi-microphone techniques can raise the recognition rate by using the spatial information of the speakers . We will compare the delay-and-sum-beamformer, different superdirective solutions and the post-filter approach. Our results show that these techniques are the right choice for hands–free speech recognition systems. Furthermore, we will give a deeper insight into the superdirective design fo r microphone arrays.

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