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<Paper uid="P98-1111">
  <Title>Unlimited Vocabulary Grapheme to Phoneme Conversion for Korean TTS</Title>
  <Section position="2" start_page="0" end_page="675" type="intro">
    <SectionTitle>
1 Introduction
</SectionTitle>
    <Paragraph position="0"> During the past few years, remarkable improvements have been made for high-quality text-to-speech systems (van Santen et al., 1997).</Paragraph>
    <Paragraph position="1"> One of the enduring problems in developing high-quality text-to-speech system is accurate grapheme-to-phoneme conversion (Divay and Vitale, 1997). It can be described as a function mapping the spelling of words to their phonetic symbols. Nevertheless, the function in some alphabetic languages needs some linguistic knowledge, especially morphological and phonological, but often also semantic knowledge.</Paragraph>
    <Paragraph position="2"> In this paper, we present a new grapheme-to-phoneme conversion method for unlimited vocabulary Korean TTS. The conversion method is divided into mainly four modules. Each module has its own linguistic knowledge. Phrase-break detection module assigns phrase breaks onto part-of-speech sequences using morphological knowledge. Word-boundaries before and after phrase breaks should not be coarticulated. So, accurate phrase-break assignments are essential in high quality TTS systems. In the morpheme-to-phoneme conversion module, boundary graphemes of each morpheme in the phrase are converted to phonemes by applying phonetic patterns which contain possible phonological changes in the boundaries of morphemes. The patterns are designed using morphological and phonotactic knowledge.</Paragraph>
    <Paragraph position="3"> Graphemes within a morpheme are converted into phonemes by CCV (consonant consonant vowel) conversion rules which are automatically extracted from a corpus. After all the conversions, phoneme connectivity table supports the grammaticality of the adjacency of two phonetic morphemes. This grammaticality comes from Korean phonology rules.</Paragraph>
    <Paragraph position="4"> This paper is organized as follows. Section 2 briefly explains the characteristics of spoken Korean for general readers. Section 3 and 4 introduces our grapheme-to-phoneme conversion method based on morphological and phonological knowledge of Korean. Section 5 shows experiment results to demonstrate the performance and Section 6 draws some conclusions.</Paragraph>
  </Section>
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