Kernel metric learning for phonetic classification

While a sound spoken is described by a handful of frame-level spectral vectors, not all frames have equal contribution for either human perception or machine classification. In this paper, we introduce a novel framework to automatically emphasize important speech frames relevant to phonetic information. We jointly learn the importance of speech frames by a distance metric across the phone classes, attempting to satisfy a large margin constraint: the distance from a segment to its correct label class should be less than the distance to any other phone class by the largest possible margin. Furthermore, an universal background model structure is proposed to give the correspondence between statistical models of phone types and tokens, allowing us to use statistical models of each phone token in a large margin speech recognition framework. Experiments on TIMIT database demonstrated the effectiveness of our framework.