19. The system of claim 11 , wherein the method further comprises: calculating the language model score based on the sound comparison between the language of the non-native speaker and the second language, including calculating a language model for the language of the non-native speaker and the second language and calculating a cross-entropy of an utterance with respect to the language model of the language of the non-native speaker inversely weighted by the cross-entropy of the utterance with respect to the language model of the second language.
19. The system of claim 11 , wherein the method further comprises: calculating the language model score based on the sound comparison between the language of the non-native speaker and the second language, including calculating a language model for the language of the non-native speaker and the second language and calculating a cross-entropy of an utterance with respect to the language model of the language of the non-native speaker inversely weighted by the cross-entropy of the utterance with respect to the language model of the second language. 20. The system of claim 19 , wherein calculating the cross-entropy of an utterance with respect to the language model of the language of the non-native speaker comprises assigning a lower score to utterances of the second language that are similar to sounds of the language of the non-native speaker, and assigning a higher score to utterances of the second language that are not similar to sounds of the language of the non-native speaker.