Thanks for the question.
audio-to-motion is fairly robust to noisy TTS and differing languages / accents. It doesn't use the raw audio as input, we first embed the audio using a pretrained wav2vec-style embedder, trained on millions of audio samples.
Saying this, we haven't properly evaluated in multiple languages, and we have heard from customers that lip-sync isn't always as good in non-english. For Cara 4 we're training on more diverse data, which will hopefully close this gap.