New Speech Synthesizer Preserves Nuances of Yoruba Language

Researchers have developed TTSYoruba, a rule-based concatenative diphone speech synthesizer specifically for the Yoruba language. This system is integrated into YorubaName.com, an online open dictionary for Yoruba personal names, making it a practical application for language preservation and accessibility.

The synthesizer processes tone-marked Yoruba text and generates audio using a meticulously crafted phonological rule system. It draws from an inventory of 651 diphone units that cover various tonal combinations, addressing the complex tonal nature of Yoruba. The detailed architecture includes logic for tonal file selection, handling nasal disambiguation, and deriving contextual rising and falling tones.

Beyond the technical implementation, the project also contributes to Yoruba orthography by proposing the adoption of caron and circumflex symbols as standard single-vowel contour tone markers. These markers are integrated into the text normalization process and the WriteYoruba keyboard tool, enhancing the digital representation and input of the language. A listener study involving 50 participants evaluated the system's performance, providing concrete data on its effectiveness.

This development is significant for Africa, particularly for Nigeria and the Yoruba-speaking diaspora, as it addresses the challenge of developing AI tools for low-resource African languages. By creating a robust text-to-speech system, it supports language preservation, improves digital accessibility, and provides a foundation for further AI applications in African linguistic contexts.