Video has become a crucial aspect of any marketing strategy. There is no argument with active users and views growing massively across video platforms. Snapchat now has 10 million active UK users. YouTube has over one billion unique monthly visitors. 100 million hours of video are viewed daily on Facebook.

The question is with sound or no sound?

This depends on the platform. You have to do what works for you and your brand. Two thirds of Snapchat is viewed with the sound on, but perhaps the short sweet nature of Snapchat means this only enhances the video experience. 

On Facebook automatically playing videos are much more common place, and sound would only serve as an annoyance unless you chose to turn it on.

Personally I think if you can share your message with AND without sound then you are in the money. If your message if being received and understood by taking into account their sound preference and habits, then it can only be good.