Hands-free human-robot communication robust to speaker´s radial position

In this paper we present a method in room transfer function (RTF) estimation, employed specifically for dereverberation in hands-free human-robot communication.We introduce a radial distance compensation scheme which significantly improved the RTF estimate robust to the speech power variation due to changes in speaker´s radial position. The proposed method is implemented in two levels; first, waveform-level compensation is executed to reflect the change in power caused by the change of radial position to the RTF. We generated possible RTF estimates within a close neighbourhood based on curve fitting. Then, we select among these estimates the optimal RTF based on acoustic model likelihood criterion, the same criterion employed in automatic speech recognition (ASR) systems. The latter is referred to as acoustic model-level compensation, which links the generated RTF to the ASR. We note that in ASR application, both waveform and acoustic models play an important role in achieving optimal performance. Thus, the synergistic effect of the two processes guarantee ASR performance improvement when used in conjunction with our ASR-based dereverberation scheme. Experimental evaluation show robustness in recognition performance when used in hands-free human-robot communication environment.