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

PCFG: inside and outside probabilities

Inside probability β

Sentence probability

Calculation of β

Outside probability α

Sentence probability

Calculation of α

PCFG Training

EM Algorithm for training

Phonetics and Phonology

Morphology to Phonology: an exercise The plural morpheme:

-s: /s/ (cats) /z/ (dogs) /iz/ (bushes)

Which sound should occur where?

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

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

Classification Manner of articulation Place of articulation Voicedness

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

Fricatives /f/ /v/ /th/ /dh/ /s/ /sh/ /zh/ /h/

Affricates /ch/ /jh/

Nasals /m/ /n/ /ng/

The plural sound Cats, racks … /s/ dogs, rags … /z/ Bushes, classes … /iz/

Hypotheses?

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/!