Method and system for assessing pronunciation difficulties of non-native speakers

• US 20060155538A1
• Filed: 01/10/2006
• Published: 07/13/2006
• Est. Priority Date: 01/11/2005
• Status: Active Grant

• Current Assignee: Educational Testing Service
• Original Assignee: Educational Testing Service
• Inventors: Higgins, Derrick, Zechner, Klaus, Lawless, Rene, Futagi, Yoko
• Granted Patent: US 8,478,597 B2
• Time in Patent Office: Days
• US Class Current: 704/246
• CPC Class Codes: G09B 19/06 Foreign languages with audible presentation of material to be studied G09B5/04
• CPC Class Codes: G10L 15/19 Grammatical context, e.g. disambiguation of the recognition hypotheses based on word sequence rules

Abstract

The present disclosure presents a useful metric for assessing the relative difficulty which non-native speakers face in pronouncing a given utterance and a method and systems for using such a metric in the evaluation and assessment of the utterances of non-native speakers. In an embodiment, the metric may be based on both known sources of difficulty for language learners and a corpus-based measure of cross-language sound differences. The method may be applied to speakers who primarily speak a first language speaking utterances in any non-native second language.

Claims

1. A method of assessing pronunciation difficulties of a non-native speaker, the method comprising:

determining one or more sources of pronunciation difficulties between a language of a non-native speaker and a second language;

assigning a weight to each source;

calculating a phonetic difficulty score based on the one or more sources and the weight assigned to each source;

calculating a language model score based on a sound comparison between the language of the non-native speaker and the second language;

normalizing the phonetic difficulty score and the language model score; and

calculating a metric from the normalized phonetic difficulty score and the normalized language model score.

2. The method of claim 1, wherein calculating the phonetic difficulty score comprises calculating a product of the number of times the source occurs in an utterance of the non-native speaker and the weight of the source.

3. The method of claim 1, wherein calculating the language model score comprises:

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 inversely weighted by the cross-entropy of the utterance with respect to the language model of the second language.

4. The method of claim 3, wherein calculating a language model for the language of the non-native speaker and the second language comprises phonetically transcribing the first language of the non-native speaker and the second language.

5. The method of claim 3, wherein calculating the cross-entropy of an utterance with respect to the language model of the first language 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.

6. The method of claim 1, wherein normalizing the phonetic difficulty score and the language model score comprises determining a normalized phonetic difficulty score and a normalized language model score such that the mean of the normalized phonetic difficulty score is equal to the mean of the normalized language model score and the standard deviation of the normalized phonetic difficulty score is equal to the standard deviation of the normalized language model score.

7. The method of claim 1, wherein calculating the metric comprises calculating the sum of the normalized phonetic difficulty score and the normalized language model score.

8. A system for assessing the pronunciation difficulties of a non-native speaker comprising:

a processor; and

a processor-readable storage medium in communication with the processor,

wherein the processor-readable storage medium contains one or more programming instructions for performing a method of assessing the pronunciation difficulties of a non-native speaker, the method comprising;

determining one or more sources of pronunciation difficulties between a language of a non-native speaker and a second language,

assigning a weight to each source,

calculating a phonetic difficulty score based on the one or more sources and the weight assigned to each source,

calculating a language model score based on a sound comparison between the language of the non-native speaker and the second language,

normalizing the phonetic difficulty score and the language model score, and

calculating a metric from the normalized phonetic difficulty score and the normalized language model score.

9. The system of claim 8, wherein calculating the phonetic difficulty score comprises calculating a product of the number of times the source occurs in an utterance of the non-native speaker and the weight of the source.

10. The system of claim 8, wherein calculating the language model score comprises:

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.

11. The system of claim 10, wherein calculating a language model for the language of the non-native speaker and the second language comprises phonetically transcribing the language of the non-native speaker and the second language.

12. The system of claim 10, wherein calculating the cross-entropy of an utterance with respect to the language model of the first language 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.

13. The system of claim 8, wherein normalizing the phonetic difficulty score and the language model score comprises determining a normalized phonetic difficulty score and a normalized language model score such that the mean of the normalized phonetic difficulty score is equal to the mean of the normalized language model score and the standard deviation of the normalized phonetic difficulty score is equal to the standard deviation of the normalized language model score.

14. The system of claim 8, wherein calculating the metric comprises calculating the sum of the normalized phonetic difficulty score and the normalized language model score.