Rare events and closed domains: Two delicate concepts in speech synthesis.
Bernd Möbius · 2001
One of the most serious challenges for speech synthesis is the systematic treatment of events in language and speech that are known to have low frequencies of occurrence. The problems that extremely unbalanced frequency distributions pose for rulebased or data-driven models are often underestimated or even unrecognized. This paper discusses these problems in the contexts of morphology, syllabification, segmental duration and unit selection, and also suggests possible solutions. The design of databases for restricted application domains, where the distributions of linguistic and phonetic factors are known, is also critically reviewed.