Hi David! If you are referring to captions automatically turning on when the video's audio is muted, such feature isn't available yet. However, you can learn more about caption settings here: https://goo.gl/xbJ9xh . Hope this helps.
Hey @TeamYouTube is there option to turn on Captions automatically (in your App) when is sound muted? Or am I missing something? I would appreciate feature like this. 

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What a sad news. I still think it's worth consider. Thanks anyway.
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