Combination of machine scores for automatic grading of pronunciation qualityCombination of machine scores for automatic grading of pronunciation quality Peer-Reviewed Journal Publication Δημοσίευση σε Περιοδικό με Κριτές 2015-11-022000enThis work is part of an effort aimed at developing computer-based systems for language instruction; we address the task of grading the pronunciation quality of the speech of a student of a foreign language. The automatic grading system uses SRI's DecipherTM continuous speech recognition system to generate phonetic segmentations. Based on these segmentations and probabilistic models we produce different pronunciation scores for individual or groups of sentences that can be used as predictors of the pronunciation quality. Different types of these machine scores can be combined to obtain a better prediction of the overall pronunciation quality. In this paper we review some of the best-performing machine scores and discuss the application of several methods based on linear and nonlinear mapping and combination of individual machine scores to predict the pronunciation quality grade that a human expert would have given. We evaluate these methods in a database that consists of pronunciation-quality-graded speech from American students speaking French. With predictors based on spectral match and on durational characteristics, we find that the combination of scores improved the prediction of the human grades and that nonlinear mapping and combination methods performed better than linear ones. Characteristics of the different nonlinear methods studied are discussed.http://creativecommons.org/licenses/by/4.0/Speech Communication302-3121-130 Horacio Franco Neumeyer Leonardo Digalakis Vasilis Διγαλακης Βασιλης Ronen Orith Elsevier Automatic pronunciation scoring Combination of scores Hidden Markov models Speech recognition Pronunciation quality assessment Language instruction systems Computer aided language learning