On robust inverse filter design for room transfer function fluctuations

Dereverberation methods based on the inverse filtering of room transfer functions (RTFs) are attractive because high deconvolution performance can be achieved. Although many methods assume that the RTFs are time-invariant, this assumption would not be guaranteed in practice. This paper deals with the problem of the sensitivity of a dereverberation algorithm based on inverse filtering. We evaluate the effect of RTF fluctuations caused by source position changes on the dereverberation performance. We focus on the filter energy with a view to making the filter less sensitive as regards these fluctuations. By adjusting three design parameters, namely, filter length, modeling delay, and regularization parameter, a dereverberation performance of up to 15 dB of the signal-to-distortion ratio could be obtained when the source position was changed with one-eighth wavelength distance, whereas conventional investigations have claimed that such a variation would cause a large degradation.