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| Workshop 2006 Calendar | Monday, November 23, 2009 |
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Dealing with Noise: Spectral Estimation, Beamforming, and Video 1:30 pm Shaffer 100 These lectures will organize classical and new ideas for acoustic noise amelioration. Specifically, the goal of these lectures is to cover the noise amelioration methods currently being tested for HMM and DBN recognizers operating on the AVICAR corpus. Lectures will be limited to one hour each; slides will be posted on the web afterward, with citations. Lecture 2: Beamforming Humans have two ears; AVICARs have seven. Scene analysis in this setting requirs the organism or computer to compute an MMSE estimate of the speech features given many partially independent noisy observations. Suppose, first, that we know the room response; in that case, the MMSE estimator of any function of the speech spectrum is given by a two-step procedure, in which the first step is a linearly constrained minimum variance LCMV beamformer. Ill show you the math, and show you a few different ways to implement LCMV. Then Ill show you that, if we don really know the room response, LCMV fails dramatically. Room response estimation is an under-constrained hard problem. Possible theoretic solutions include independent components analysis ICA and backward-LCMV. A practical stopgap solution with pretty good results is a delay-and-sum beamformer. |
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