Speak Subtitles for YouTube
Reads YouTube subtitles out loud with synthetic voices in many languages, so you can listen to a video instead of reading captions.
Chrome extension
Translates the subtitles of YouTube videos and plays a dubbed voice track in your language, for videos that already have captions.
TransMonkey YouTube Translator translates a YouTube video's subtitles and plays a synchronised dubbed voice track in your chosen language. It is for viewers who want to watch foreign-language videos as if they were narrated in their own language.
Open a YouTube video that has captions, click Translate Video under the player, choose your language and save, then click the icon again to start playback with dubbing.
It only works on YouTube videos that already have subtitles; if the CC button is greyed out, the video cannot be translated.