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Features for Factored Language Models for Code-Switching Speech

Features for Factored Language Models for Code-Switching Speech. Heike Adel, Katrin Kirchhoff, Dominic Telaar , Ngoc Thang Vu, Tim Schlippe , Tanja Schultz. Outline. Introduction Motivation Seame Corpus Main Contributions Factored Language Models

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Features for Factored Language Models for Code-Switching Speech

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  1. Features for Factored Language Models for Code-Switching Speech Heike Adel, Katrin Kirchhoff, Dominic Telaar, Ngoc Thang Vu, Tim Schlippe, Tanja Schultz

  2. Outline • Introduction • Motivation • Seame Corpus • Main Contributions • Factored Language Models • Features for Code-Switching Speech • Experiments • Conclusion • Summary Features for Factored Language Models for Code-Switching Speech

  3. Motivation • Code-Switching (CS) = speechwithmorethanonelanguage • Exists in multilingual communitiesoramongimmigrants Challenges: multilingual modelsandCS trainingdatanecessary Features for Factored Language Models for Code-Switching Speech

  4. SEAME corpus • SEAME = South East Asia Mandarin-English • Conversational speech, recorded from Singaporean and Malaysian speakers by [1] Challenges • much CS per utterance (Æ: 2.6) • short monolingual segments (mostly less than 1 sec, 2-4 words) • not much training data for LM (575k words) [1] Lyu, D.C. et al.,2010Originally used: research project ‘Code-Switch‘ (NTU and KIT) other particle EN MAN Features for Factored Language Models for Code-Switching Speech

  5. Main contributions • Investigation of different featuresfor Code-Switchingspeech • Integration offactoredlanguagemodelsinto a dynamicone-pass decoder Features for Factored Language Models for Code-Switching Speech

  6. Factored Language Models (FLMs) [2] • Idea: word = feature bundle • Good e.g. in the case of • Rich morphology • Few training data=> applicable to CS task • Generalized backoff F | F1 F2 F3 F | F1 F2 F | F2 F3 F | F1 F3 F | F1 F | F2 F | F3 F [2] Bilmes, J. and Kirchhoff, K., 2003 Features for Factored Language Models for Code-Switching Speech

  7. Features: Words, POS, LID • Problems: • POS tagging of CS speech: challenging • Accuracy of POS tagger: unknown •  different clustering method may be more robust Features for Factored Language Models for Code-Switching Speech

  8. Features: Brown Word Clusters • Clusters based on word distributions in text [3] • minimize average mutual information loss • Best number of classes in terms of PPL: 70 • So far: clusters based on syntax or word distributions  next step: semantic features • [3] Brown, P.F. Et al. ,1992 Features for Factored Language Models for Code-Switching Speech

  9. Features: Open Class Words • Definition: content words, e.g. nouns, verbs, adverbs • “open” because class can be extended with new words, e.g. “Bollywood”  open class words indicate semantic of sentence Features for Factored Language Models for Code-Switching Speech

  10. Features: Open Class Word Clusters • Idea: • Semantic clusters in comparison to distribution based clusters (oc Brown clusters) OC word 1, OC word 2, OC word 3, …, OC word 8, OC word 9 OC word 2 OC word 5 OC word 9 Topic c Topic a OC word 4 OC word 7 OC word 8 OC word 1 OC word 3 OC word 6 Topic b Features for Factored Language Models for Code-Switching Speech

  11. Features: Semantic OC Word Clusters • Clustering of open class word vectors • RNNLMs learn syntactic and semantic similarities [4] • RNNLMs represent words as vectors  apply clustering to these word vectors • k-means clustering • spectral clustering [4] Mikolov, T. et al., 2013 Features for Factored Language Models for Code-Switching Speech

  12. Features: Semantic OC Word Clusters • Experiments with different • Clustering methods • Brown, k-means, Spectral Clustering • Monolingual and bilingual clusters • Monolingual Clusters • Based on English and Mandarin Gigaword data (2005) • Bilingual Clusters • Based on CS text • Mixed lines of Gigaworddata • different numbers of clusters  Lowest perplexity (247.24, but unclusteredoc words: 247.18): • Spectral Clustering • Bilingual Clusters • 800 OC word clusters Features for Factored Language Models for Code-Switching Speech

  13. FLMs: Decoding Experiments • Interpolation weight of FLM and n-gram FLM weight Features for Factored Language Models for Code-Switching Speech

  14. FLMs: Decoding Experiments (2) • Decoding results Features for Factored Language Models for Code-Switching Speech

  15. Conclusion • Summary • Best features in termsof FLM perplexity: words + POS + Brown clusters + ocwords • Relative PPL reductionofupto 10.8% (eval) • Best features in termsof MER:words + POS + Brown clusters (+ occlusters) • Relative MER reductionofupto 3.4% (eval) Features for Factored Language Models for Code-Switching Speech

  16. Thank you for your attention! Features for Factored Language Models for Code-Switching Speech

  17. References Features for Factored Language Models for Code-Switching Speech

  18. References Features for Factored Language Models for Code-Switching Speech

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