The training modules do not require sound, but it is strongly recommended that you do have sound. There are live-action demonstrations and we find it provides a better learning experience overall.
There are captions for all parts of the courses, including the live-action demonstrations portion, so any users with hearing disabilities or without sound capabilities can still complete the course with 100% of the information as contained in the audio portions of the course.
Sound not working? Check out our training troubleshooting article, here.