Recurrent deep stacking networks for supervised speech separation

Supervised speech separation algorithms seldom utilize output patterns. This study proposes a novel recurrent deep stacking approach for time-frequency masking based speech separation, where the output context is explicitly employed to improve the accuracy of mask estimation. The key idea is to incorporate the estimated masks of several previous frames as additional inputs to better estimate the mask of the current frame. Rather than formulating it as a recurrent neural network (RNN), which is potentially much harder to train, we propose to train a deep neural network (DNN) with implicit deep stacking. The estimated masks of the previous frames are updated only at the end of each DNN training epoch, and then the updated estimated masks provide additional inputs to train the DNN in the next epoch. At the test stage, the DNN makes predictions sequentially in a recurrent fashion. In addition, we propose to use the L1 loss for training. Experiments on the CHiME-2 (task-2) dataset demonstrate the effectiveness of our proposed approach.