Rules for irregularities in speech production of American English

Abstract

General rules for production of English phonemes may be studied very effectively by statistical methods. The rules have numerous exceptions, however, involving special treatment of sometimes infrequently occurring conditions. The problem is to identify these exceptions, and then to find enough examples to characterize them. Speech synthesis is especially suitable for this kind of exploratory study. When synthesized utterances are substantially correct, exceptions stand out clearly, as mispronounced words. In our synthesis, a program for regular timing and allophone selection is followed by a set of rewriting rules to handle exceptions. In using the system, when utterances are found for which the rules are inadequate, the program allows quick examination of similar phrases, and interactive editing at the segment level to evaluate potential rule changes. New rules are easily added, or existing ones further qualified. Using this method, we have developed quantitative rules for nasal assimilation, flaps, changes within cluster, syllabic consonants, context-dependent vowel glides, and other adjustments to prevent devoicing and slurring of weak syllables. The rules are nonrecursive, LR1 at the segment level, and programmable in about 80 FORTRAN logical IFs. The oral paper will summarize these rules. Part of the presentation will be in synthetic speech.