On the Issue of Calibration in DNN-based Speaker Recognition Systems

This article is concerned with the issue of calibration in the context of Deep Neural Network (DNN) based approaches to speaker recognition. DNNs have provided a new standard in technology when used in place of the traditional universal background model (UBM) for feature alignment, or to augment traditional features with those extracted from a bottleneck layer of the DNN. These techniques provide extremely good performance for constrained trial conditions that are well matched to development conditions. However, when applied to unseen conditions or a wide variety of conditions, some DNN-based techniques offer poor calibration performance. Through analysis on both PRISM and the recently released Speakers in the Wild (SITW) corpora, we illustrate that bottleneck features hinder calibration if used in the calculation of first-order Baum Welch statistics during i-vector extraction. We propose a hybrid alignment framework, which stems from our previous work in DNN senone alignment, that uses the bottleneck features only for the alignment of features during statistics calculation. This framework not only addresses the issue of calibration, but provides a more computationally efficient system based on bottleneck features with improved discriminative power.