Acoustical Properties of Word Boundaries in English

Abstract

From empirical studies to adjust the durations of phonemes in rule-synthesized speech, it is found that the durations of phonemes at the word junctures separate into three clearly defined categories. These duration classes are taken to define three types of word boundary: weak, intermediate, and strong. The weak boundary occurs between monosyllabic functional words such as “in-the, is-the”, and “it-is.” Consonant durations are quite the same as inside polysyllabic words. The strong boundary occurs between major content words (roughly, words that would be capitalized in a title). It is characterized by quite-lengthened single consonants and medium-duration initial consonants of clusters. If the initial syllable of the word following the juncture carries primary stress, initial plosives will have stronger bursts and increased aspiration. Initial primary-stressed vowels will have an unaspirated devoiced portion resembling a glottal stop. The intermediate boundary occurs between compound words and at junctures between content words and certain semifunctional words, like “such,” “there,” “other,” and “most.” Changes of speech rate do not strongly affect definitions of the strong and intermediate boundaries. As rate increases, weak boundaries selectively replace strong ones, often without progression through the intermediate level.