You will probably find that most people use their phones in silent mode, and vibrating mode. Media (such as video) is often watched in silent mode as it is played back.
Smartphones are now our TV sets, newspapers and diaries, but they are also our way of escaping reality. With video, sound is an integral part of information exchange – but more and more people are choosing to watch videos silently, and the Mute Generation, as it is often called, watches hours of video in silent mode – but does it make sense to produce video without sound? Of course! But only with subtitles. Public engagement with subtitled videos is higher than for videos without subtitles, in a world where 85% people use their smartphones in silent mode.
However the use of automated subtitling can cause problems for brands; it is unreliable and homophone words are inserted by mistake, often to the detriment of brand image.