As of now, Chrome is blocking sound for videos that are played automatically.
This function should come out in January, but was postponed. From now on, Google Chrome will no longer play sound with videos that start automatically, so you have to turn on the sound yourself. This is in any case a best practice to implement yourself.
It is also a good idea, especially if you use programmatic video ads for your marketing purposes, to measure the audibility of your campaigns. With the audibility metrics you can, for example, see how many people have switched on the sound.
A good overview of the possible metrics at Video and Audio is shown in DoubleClick’s overview below:
Another best practice is to optimize your videos for “sound-off”. That means: even if the sound is off, a user must be able to understand what your video is about. This can be done with subtitles, but also with the image itself.