EAN: 9783642232497

SPRINGERBRIEFS IN ELECTRICAL AND COMPUTER ENGIN...

This work addresses this problem in the short-time Fourier transform (STFT) domain. We divide
the general problem into five basic categories depending on the number of microphones being
used and whether the interframe or interband correlation is considered. The first category
deals with the single-channel problem where STFT coefficients at different frames and frequency
bands are assumed to be independent. In this case  the noise reduction filter in each frequency
band is basically a real gain. Since a gain does not improve the signal-to-noise ratio (SNR)
for any given subband and frame  the noise reduction is basically achieved by liftering the
subbands and frames that are less noisy while weighing down on those that are more noisy. The
second category also concerns the single-channel problem. The difference is that now the
interframe correlation is taken into account and a filter is applied in each subband instead of
just a gain. The advantage of using the interframe correlation is that we can improve not only
the long-time fullband SNR  but the frame-wise subband SNR as well. The third and fourth
classes discuss the problem of multichannel noise reduction in the STFT domain with and without
interframe correlation  respectively. In the last category  we consider the interband
correlation in the design of the noise reduction filters. We illustrate the basic principle for
the single-channel case as an example  while this concept can be generalized to other
scenarios. In all categories  we propose different optimization cost functions from which we
derive the optimal filters and we also define the performance measures that help analyzing
them.

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