Abstract:As a type of deep neural network (DNN) based low-dimensional feature,bottleneck feature (BNF) has achieved great success in continuous speech recognition. However, the existing of bottleneck layer reduces the frame accuracy of output layer when training a bottleneck deep neural network (BNDNN), which in return has a bad impact on the performance of bottleneck feature. To solve this problem, a nonnegative matrix factorization based low-dimensional feature extraction approach using DNN without bottleneck layer is proposed in this paper. Specifically, semi-nonnegative matrix factorization and convex-nonnegative matrix factorization algorithms are applied to hidden-layer weights matrix to obtain a basis matrix as the new feature-layer weights matrix, and a new type of feature is extracted by forward passing input data without setting a bias vector in the new feature-layer. Experiments show that the feature has a relatively stable pattern around different tasks and network structures. For corpus with enough training data, the proposed features have almost the same recognition performance with conventional bottleneck feature. Under low-resource environment, the recognition accuracy of the new feature-tandem system outperforms both DNN hybrid system and bottleneck-tandem system obviously.