@Dr. Golden Welcome to Microsoft Q&A Forum, Thank you for posting your query here!
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To answer your question, currently the built-in avatar characters are only limited to the ones provided (Asian).
However, as an alternative, you can leverage the Custom Text to Speech avatar .
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Custom text to speech avatar
allows you to create a customized, one-of-a-kind synthetic talking avatar for your application. With custom text to speech avatar, you can build a unique and natural-looking avatar for your product or brand by providing video recording data of your selected actors.
More info here.
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On a side note
: We are working on adding more voice characters. This is in our roadmap. However, we don't have an ETA on when this would be available. Once this new feature is added, we will update it in this documentation.
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Hope this helps. If you have any follow-up questions, please let me know. I would be happy to help.
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