Discriminative transformations of speech features based on minimum classification error

Feature extraction is an important step in pattern classification and speech recognition. Extracted features should discriminate classes from each other while being robust to the environmental conditions such as noise. For this purpose, some transformations are applied to features. In this paper, we propose a framework to improve independent feature transformations such as PCA (Principal Component Analysis), and HLDA (Heteroscedastic LDA) using the minimum classification error criterion. In this method, we modify full transformation matrices such that classification error is minimized for mapped features. We do not reduce feature vector dimension in this mapping. The proposed methods are evaluated for continuous phoneme recognition on clean and noisy TIMIT. Experimental results show that our proposed methods improve performance of PCA, and HLDA transformation for MFCC in both clean and noisy conditions.