Joint training of DNNs by incorporating an explicit dereverberation structure for distant speech recognition

We explore joint training strategies of DNNs for simultaneous dereverberation and acoustic modeling to improve the performance of distant speech recognition. There are two key contributions. First, a new DNN structure incorporating both dereverberated and original reverberant features is shown to effectively improve recognition accuracy over the conventional one using only dereverberated features as the input. Second, in most of the simulated reverberant environments for training data collection and DNN-based dereverberation, the resource data and learning targets are high-quality clean speech. With our joint training strategy, we can relax this constraint by using large-scale diversified real close-talking data as the targets which are easy to be collected via many speech-enabled applications from mobile internet users, and find the scenario even more effective. Our experiments on a Mandarin speech recognition task with 2000-h training data show that the proposed framework achieves relative word error rate reductions of 9.7 and 8.6 % over the multi-condition training systems for the cases of single-channel and multi-channel with beamforming, respectively. Furthermore, significant gains are consistently observed over the pre-processing approach using simply DNN-based dereverberation.