Improving robustness of deep neural networks via spectral masking for automatic speech recognition

The performance of human listeners degrades rather slowly compared to machines in noisy environments. This has been attributed to the ability of performing auditory scene analysis which separates the speech prior to recognition. In this work, we investigate two mask estimation approaches, namely the state dependent and the deep neural network (DNN) based estimations, to separate speech from noises for improving DNN acoustic models´ noise robustness. The second approach has been experimentally shown to outperform the first one. Due to the stereo data based training and ill-defined masks for speech with channel distortions, both methods do not generalize well to unseen conditions and fail to beat the performance of the multi-style trained baseline system. However, the model trained on masked features demonstrates strong complementariness to the baseline model. The simple average of the two system´s posteriors yields word error rates of 4.4% on Aurora2 and 12.3% on Aurora4.