Most of the videos don't have sound because the video maker muted it during the upload. This could be related to the bad sound quality, due to the wind, the road environment, etc. However, coaching videos include sound as the coach gives instructions but also add some music in the background.
In case you don't have sound in the app, make sure that :
- This video has sound
- You don't have a physical 'mute' button (especially on Apple devices)
- The volume is high enough in your sound settings
- In the Kinomap app, you didn't mute some sounds: