Automatically mute audio when playing embedded videos from external sites

Hi all!

Me again with another question about embedded videos from external sites. 

I'm struggling with finding a straightforward way to automatically mute audio when a user clicks to play a video that is inserted from an external site (i.e. not uploaded directly into storyline). Trigger wizard doesn't see the video object as media so I can't assign the usual triggers etc to stop the audio when they user clicks to play the video in YT. 

The closest I can get is by creating a screenshot of the video with a play button, then uploading the video to autoplay in a layer which does add quite a bit of a workaround, is there anything obvious I might be missing so I don't have to do this for every video in quite a video-content heavy piece of elearning?

Thanks!