Reference-Free Metric Targets Lexical Tone Evaluation in Multilingual TTS
A new arXiv paper proposes a reference-free way to measure whether text-to-speech systems render lexical tone correctly in languages where pitch changes word meaning. The authors note that standard character error rate scoring misses such errors, using Yorùbá words like "ọkọ" (husband), "ọkọ̀" (vehicle) and "ọkọ́" (hoe), which differ only by tone, as an illustration. The work aims to give a budget-friendly evaluation option for massively multilingual speech systems.