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Pushpak Bhattacharyya CSE Dept., IIT Bombay 29 th March, 2011

CS460/626 : Natural Language Processing/Speech, NLP and the Web (Lecture 31–Inside and Outside probabilities; PCFG training; start of phonetics and phonology). Pushpak Bhattacharyya CSE Dept., IIT Bombay 29 th March, 2011. PCFG: inside and outside probabilities. Inside probability β.

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Pushpak Bhattacharyya CSE Dept., IIT Bombay 29 th March, 2011

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  1. CS460/626 : Natural Language Processing/Speech, NLP and the Web(Lecture 31–Inside and Outside probabilities; PCFG training; start of phonetics and phonology) Pushpak BhattacharyyaCSE Dept., IIT Bombay 29th March, 2011

  2. PCFG: inside and outside probabilities

  3. Inside probability β Sentence probability

  4. Calculation of β

  5. Outside probability α Sentence probability

  6. Calculation of α

  7. PCFG Training

  8. EM Algorithm for training

  9. Phonetics and Phonology

  10. Morphology to Phonology: an exercise • The plural morpheme: • -s: • /s/ (cats) • /z/ (dogs) • /iz/ (bushes) • Which sound should occur where?

  11. Phonetics and Phonology • Phonetics: The study of speech sounds • Articulatory • Acoustic • Auditory • Phonology: the structure and patterning of sounds • Phonetic Transcription: • A writing system for representing speech sounds

  12. The need for phonetic transcription • Eccentricity of English Spelling • Put/Putt • Car/Kite • Rough/Puff • Fish can be spelt ‘ghoeti’. How? • A language for talking about other/newly discovered languages • New languages without a writing system are discovered often

  13. Classification • Manner of articulation • Place of articulation • Voicedness

  14. Stops • /p/ - voiceless bilabial • /b/ - voiced bilabial • /t/ - voiceless alveolar • /d/ - voiced alveolar • /k/ - voiceless velar • /g/ - voiced velar

  15. Fricatives • /f/ • /v/ • /th/ • /dh/ • /s/ • /sh/ • /zh/ • /h/

  16. Affricates • /ch/ • /jh/

  17. Nasals • /m/ • /n/ • /ng/

  18. The plural sound • Cats, racks … /s/ • dogs, rags … /z/ • Bushes, classes … /iz/ Hypotheses?

  19. A kudo to each of you! • Kudos: pronounced with an /s/ sound at the end • Misinterpreted as a plural • One kudo, many kudos • Pronunciation becomes kudo/z/!

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