Estimation of the Optimum System Delay for Speech Dereverberation by Inverse Filtering

Equalization of room impulse responses is an attractive approach for dereverberation of speech signals in a hands-free scenario. In this contribution we address the choice of the delay which has to be introduced in leastsquares equalization approaches for a maximum amount of dereverberation. Since designing one equalizer (EQ) for each possible delay and choosing the best one is computationally inefficient we evaluate the dependence of the optimum equalizer delay of various measures characterizing room impulse responses (RIRs). A high correlation was found between the so-called central time of the room impulse response and the optimum equalizer delay. Since the central time can be determined based on estimates of the initial peak of the RIR and the room reverberation time, we propose to use a very short filter for system identification and an estimate of the room reverberation time to identify the optimum equalizer delay. The proposed approach prevents a low performance of the equalizer which may occur for an improperly chosen delay by automatically estimating the optimum delay.