Synthesis of Arabic from short sound clusters

Abstract

This article describes an unrestricted vocabulary text-to-speech (TTS) conversion system for the synthesis of Standard Arabic (SA) speech. The system uses short phonetic clusters that are derived from the Arabic syllables to synthesize Arabic. Basic and phonetic variants of the synthesis units are defined after qualitative and quantitative analyses of the phonetics of SA. A speech database of the synthesis units and their phonetic variations is created and the units are tested to control their segmental quality. Besides the types of synthesis unit used, their enhancement with phonetic variants, and their segmental quality control, the production of good quality speech also depends on waveform analysis and the method used to concatenate the synthesis units together. Waveform analysis is needed to condition the selected synthesis units at their junctures to produce synthesized speech of better quality. The types of speech juncture between contiguous units, the phonetic characteristics of the sounds surrounding the junctures and the concatenation artifacts occurring across the junctures are important and will be discussed. The results of waveform analysis and smoothing algorithms will be presented. The intelligibility of synthesized Arabic by a standard intelligibility test method that is adapted to suit the Arabic phonetic characteristics and scoring the results of the tests will also be dealt with.