Letter to Phoneme Letter to Phoneme AlignmentAlignment

Using Graphical Models

N. Bolandzadeh, R. Rabbany

Dept of Computing ScienceUniversity of Alberta

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Text to Speech Text to Speech ProblemProblem

Conversion of Text to Speech: TTS

◦Automated Telecom Services◦E-mail by Phone◦Banking Systems◦Handicapped People

2

PronunciationPronunciation

Pronunciation of the words Dictionary Words Non-Dictionary Words

Phonetic analysis Dictionary lookup?

Language is alive, new words addProper Nouns

Machine Learning higher accuracyL 2 P alignment is needed

3

4

ProblemProblemLetter to Phoneme Alignment

◦ Letter: c a k e

◦ Phoneme: k ei k

4

L2P

Automatic Speech Recognition

&

Spelling Correction

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It's not Trivial! It's not Trivial! why?why?

No Consistency◦City / s /◦Cake / k /◦Kid / k /

No Transparency◦K i d (3) / k i d / (3) ◦S i x (3) / s i k s / (4)◦Q u e u e (5) / k j u: / (3)◦A x e (3) / a k s / (3)

5

FrameworkFramework

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Brick brIkBrightening br2tHINBritishbrItISBronx brQNksBugle bjugPBuoy b4

b|r|i|ck| b|r|I|k|b|r|ig|ht|en|i|ng| b|r|2|t|H|I|N|b|r|i|t|i|sh| b|r|I|t|I|S|b|r|o|n|x| b|r|Q|N|ks|b|u|g|le| b|ju|g|P|bu|oy| b|4|

EvaluationEvaluationNo Aligned DictionaryUnsupervised LearningPreviously aligner was tied with a

generator

Evaluation on percentage of correctly predicted phonemes and words

7

Model of our problemModel of our problem

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mn pppPlllL ...... 2121

2|||,|

,

...

),|(maxarg

21

ii

iii

k

Abest

PL

PLa

aaaA

PLAPA

B | r | i | t | i | sh |B | r | I | t | I | S |

Static Model, StructureStatic Model, StructureIndependent sub alignments

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l1 l2

p1 p2

a1

k

iiii PLaPAP

1

),|()(

l3 l4

p3 p4

a2

ln-1 ln

pm-1

pm

ak

Static Model, LearningStatic Model, LearningEM

◦Initialize Parameters◦Expectation Step:

Parameters Alignments

◦Maximization Step: Alignments Parameters

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Result of Static ModelResult of Static Model

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Method Letters Words

Static Model

81.34% 43.5%

Dynamic ModelDynamic Model

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Sequence of dataUnrolled model for T=3 slices

l1 l2

p1 p2

a1

l3 l4

p3 p4

a2

l5 l6

p5 p6

ak

QuestionsQuestions

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