Synthesizing Allophonic Glottalization

Abstract

This chapter presents a method for synthesizing allophonic glottalization. The method is motivated by empirical studies of the phonological context for glottalization and of its acoustic consequences. A baseline study of production explored glottalization in two situations : (1) vowel-vowel hiatus across a word boundary, and (2) voiceless stops before sonorants. The study showed that allophonic glottalization depends on the segmental context, syllabic position, and phrasal prosody. Successful synthesis of contextually appropriate glottalization requires an architecture with a running window over a fully parsed phonological structure, or its effective equivalent. The signal coding used was based on the source model and cascade formant synthesis presented by [Kla87]. Synthesis of glottalization can be achieved by lowering the fundamental frequency (pulsive F function serving as0), keeping all other factors in formant synthesis constant. Thus, any synthesis procedure that has the ability to directly control F0 will be able to reproduce glottalization in a similar manner. For fully natural, theoretically correct synthesis, additional control parameters are needed to control the length of the glottal pulse and for spectral tilt.