Unsupervised Linear Discriminant Analysis for Supporting DPGMM Clustering in the Zero Resource Scenario

In this work we make use of unsupervised linear discriminant analysis (LDA) to support acoustic unit discovery in a zero resource scenario. The idea is to automatically find a mapping of feature vectors into a subspace that is more suitable for Dirichlet process Gaussian mixture model (DPGMM) based clustering, without the need of supervision. Supervised acoustic modeling typically makes use of feature transformations such as LDA to minimize intra-class discriminability, to maximize inter-class discriminability and to extract relevant informations from high-dimensional features spanning larger contexts. The need of class labels makes it difficult to use this technique in a zero resource setting where the classes and even their amount are unknown. To overcome this issue we use a first iteration of DPGMM clustering on standard features to generate labels for the data, that serve as basis for learning a proper transformation. A second clustering operates on the transformed features. The application of unsupervised LDA demonstrably leads to better clustering results given the unsupervised data. We show that the improved input features consistently outperform our baseline input features