Syllable: A self-contained unit to model pronunciation variation

In this paper, we demonstrate the potential of incorporating syllable-level information in acoustic modeling. The unit of syllable is not rigorously defined, which leads to a problem for its use. In this study, we derive syllable structures from the sonorant-band intensity profile of speech signal. We analyze the error statistics of a phone-based context-dependent speech recognizer and find interesting error patterns. Phone errors mainly occur inside a syllable but not at syllable boundaries. Pronunciation variation can thus be regarded as the replacement of phonetic elements within the time span of a solitary syllable. We apply simple rules to model the pronunciation variation phenomenon. A lexical modeling approach modifies the bi-phone transcription in the dictionary. It leads to a significant increase of phone correctness. The results shed light on a more intuitive and direct approach to model pronunciation variation within the scope of syllables.