A COMPARISON OF LETTER-TO-SOUND CONVERSION TECHNIQUES FOR ENGLISH TEXT-TO-SPEECH SYNTHESIS

Abstract

this paper are those of Elovitz et al. [2] obtained by anonymous ftp from directory comp.speech/synthesis at svr-ftp.eng.cam.ac.uk. 2.2 Pronunciation by Analogy Pronunciation by analogy (PbA) exploits the phonological knowledge implicitly contained in a dictionary of words and their corresponding pronunciations. The underlying idea is that a pronunciation for an unknown word is assembled by matching substrings of the input to substrings of known, lexical words, hypothesising a partial pronunciation for each matched substring from the phonological knowledge, and concatenating the partial pronunciations. The variant of PbA evaluated here is based on Dedina and Nusbaum's PRONOUNCE [4], but with several further enhancements as detailed by Marchand and Damper [5]. In PRONOUNCE, a data structure called the pronunciation lattice is built from matching substrings in the input word and the dictionary entries. This is a graph containing information about the position and total number of matched substrings, and their partial pronunciations. A possible pronunciation for the input string then corresponds to a complete path through its lattice, with the output string assembled by concatenating the phoneme labels on the nodes/arcs in the order that they are traversed. (Different paths can, of course, correspond to the same pronunciation.) Scoring of candidate pronunciation uses two heuristics in PRONOUNCE. If there is a unique shortest path, then the pronunciation corresponding to this path is taken as the output. If there are tied shortest paths, then the pronunciation corresponding to the best scoring of these is taken as the output. The version of PbA evaluated here features several enhancements over PRONOUNCE. First, we use `full' pattern matching between input letter string and d...