If they can’t truly can not hear, subtitles if available, are the only option.
So now you can see that because for a large part of the time, mobile users can’t effectively hear sound, this is why subtitles are now so very important.
For subtitling videos, you have two different options.
The first is known as soft subtitles, which is where you have a separate subtitle text file created, that you upload along with your video, which allows users to turn them on and off as they wish.
Currently on Facebook, if a subtitle track has been supplied, it will automatically display subtitles on a mobile device if sound is not playing.
The second option is what’s known as hard subtitles, and this is where they are are permanently overlaid on top of the video.