Stress Assignment in Letter to Sound Rules for Speech Synthesis

This paper will discuss how to determine word stress from spelling. Stress assignment is a well-established weak point for many speech synthesizers because stress dependencies cannot be determined locally. It is impossible to determine the stress of a word by looking through a five or six character window, as many speech synthesizers do. Wellknown examples such as degrade / dbgradl, tion and tMegraph / telegraph5 demonstrate that stress dependencies can span over two and three syllables. This paper will pre~nt a principled framework for dealing with these long distance dependencies. Stress assignment will be formulated in terms of Waltz' style constraint propagation with four sources of constraints: (1) syllable weight. (2) part of speech. (3) morphology and (4) etymology. Syllable weight is perhaps the most interesting, and will be the main focus of this paper. Most of what follows has been implemented.