Optimization of the DET curve in speaker verification

Speaker verification systems are, in essence, statistical pattern detectors which can trade off false rejections for false acceptances. Any operating point characterized by a specific tradeoff between false rejections and false acceptances may be chosen. Training paradigms in speaker verification systems however either learn the parameters of the classifier employed without actually considering this tradeoff, or optimize the parameters for a particular operating point exemplified by the ratio of positive and negative training instances supplied. In this paper we investigate the optimization of training paradigms to explicitly consider the tradeoff between false rejections and false acceptances, by minimizing the area under the curve of the detection error tradeoff curve. To optimize the parameters, we explicitly minimize a mathematical characterization of the area under the detection error tradeoff curve, through generalized probabilistic descent. Experiments on the NIST 2008 database show that for clean signals the proposed optimization approach is at least as effective as conventional learning. On noisy data, verification performance obtained with the proposed approach is considerably better than that obtained with conventional learning methods.