Abstract
A method for estimating the relevant quantities in a multi-channel Wiener filter (MWF) for speech dereverberation is proposed for a microphone system consisting of a local microphone array (LMA) and a single external microphone (XM). Typically these MWF quantities can be estimated by considering pre-whitened correlation matrices with a dimension equal to the number of microphones in the system. By following another procedure involving a pre-whitening-transformation operation, it will be demonstrated that when a priori knowledge of the relative transfer function (RTF) vector pertaining to only the LMA is available and when the reverberant component of the signals received by the LMA is uncorrelated with that of the XM, the MWF quantities may be alternatively estimated from a 2 x 2 matrix. Simulations confirm that using such an estimate results in a similar performance to that obtained by using the higher-dimensional correlation matrix.