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Development of the MTF-based speech dereverberation method using adaptive time-frequency division

We previously proposed a speech dereverberation method based on the modulation transfer function (MTF) concept. In that model, power envelopes and carriers are decomposed from a reverberant speech signal using a constant-bandwidth filterbank and then are restored in each respective channel using, respectively, power envelope inverse filtering and a carrier regeneration method. In this paper, we explain how the model can be improved through adaptive time-frequency division using a reconstructed filterbank that depends on each speech signal. In addition, the “buzz” sounds caused by the carrier regeneration process of our previous model can be removed by controlling the group delay in the carrier. We have carried out 15,000 simulations of dereverberation for reverberant speech signals to objectively evaluate the improved model. We also subjectively evaluated the model via listening tests (sound quality, reverberation, and word intelligibility). Results of both evaluations show that in addition to reducing the averaged log-spectrum distortion by about 1 dB the improved model reduces the loss of speech intelligibility caused by reverberation by 30 %.