ASSIGNMENT OF SYLLABLE STRESS IN A DEl\USYLLABLE-BASED TEXT-TO-SPEECH SYNTHESIS SYSTEl\f

The purpose of this paper is to · describe an algorithm that has been developed to determine the stress pattern of polysyllabic words in English. Stress is one determinant of word pronunciation in English. and the algorithm is an important component of a demisyllable-based text-to-speech synthesis system. The algorithm described here is a computationally efficient and accurate system for assigning primary stress to English words. 1. INTRODUCfION The conversion of written English text into intelligible speech by means of a com puter involves a number of different steps. The first of these is the conversion of text to some abstract linguistic form that represents the pronunciation of each word in the text. Within this stage there are two components that rely on each other in obtaining a high degree of accuracy for later stages in the synthesis procedure. The first of these is the conversion of English letters into phonemes. The second is the determination of the stress pattern for polysyllabic words. This paper describes an algorithm that has been developed to predict English stress. The algorithm is currently being used in a demisyllable-based text-to-speech synthesis system (Eady et. al. • 1988). 2. SRESS IN ENGLISH The correct assignment of stress to words in English is an important aspect of any text-to-speech synthesis system. Stress in English can be defined as the relative prom inence of the syllables in a word. and it has an important influence on pronunciation. For example. it is a difference in stress that causes the difference in pronunciation between the noun "OBject " (with primary stress located on the first syllable) and the verb"obJB;'['f (with primary stress located on the second syllable). This difference in stress is mani fested by variations in the pitch. duration and amplitUde of each syllable in a word. There are varying degrees of stress in English words and the main concern of this paper is to determine the placement of the primary or main stress in words (i.e. • the most prom inent syllable)