Automatic classification of unequal lexical stress patterns using machine learning algorithms

Technology based speech therapy systems are severely handicapped due to the absence of accurate prosodic event identification algorithms. This paper introduces an automatic method for the classification of strong-weak (SW) and weak-strong (WS) stress patterns in children speech with American English accent, for use in the assessment of the speech dysprosody. We investigate the ability of two sets of features used to train classifiers to identify the variation in lexical stress between two consecutive syllables. The first set consists of traditional features derived from measurements of pitch, intensity and duration, whereas the second set consists of energies of different filter banks. Three different classifiers were used in the experiments: an Artificial Neural Network (ANN) classifier with a single hidden layer, Support Vector Machine (SVM) classifier with both linear and Gaussian kernels and the Maximum Entropy modeling (MaxEnt). these features. Best results were obtained using an ANN classifier and a combination of the two sets of features. The system correctly classified 94% of the SW stress patterns and 76% of the WS stress patterns.