Modeling prosodic feature sequences for speaker recognition

We describe a novel approach to modeling idiosyncratic prosodic behavior for automatic speaker recognition. The approach computes various duration, pitch, and energy features for each estimated syllable in speech recognition output, quantizes the features, forms N-grams of the quantized values, and models normalized counts for each feature N-gram using support vector machines (SVMs). We refer to these features as "SNERF-grams" (N-grams of Syllable-based Nonuniform Extraction Region Features). Evaluation of SNERF-gram performance is conducted on two-party spontaneous English conversational telephone data from the Fisher corpus, using one conversation side in both training and testing. Results show that SNERF-grams provide significant performance gains when combined with a state-of-the-art baseline system, as well as with two highly successful long-range feature systems that capture word usage and lexically constrained duration patterns. Further experiments examine the relative contributions of features by quantization resolution, N-gram length, and feature type. Results show that the optimal number of bins depends on both feature type and N-gram length, but is roughly in the range of 5-10 bins. We find that longer N-grams are better than shorter ones, and that pitch features are most useful, followed by duration and energy features. The most important pitch features are those capturing pitch level, whereas the most important energy features reflect patterns of rising and falling. For duration features, nucleus duration is more important for speaker recognition than are durations from the onset or coda of a syllable. Overall, we find that SVM modeling of prosodic feature sequences yields valuable information for automatic speaker recognition. It also offers rich new opportunities for exploring how speakers differ from each other in voluntary but habitual ways. (c) 2005 Elsevier B.V. All rights reserved.