The Hazard Perception app includes sound only in the following two states:
- While playing the introduction video after "Introduction" is selected from the main menu.
- When reviewing a hazard perception clip, after first viewing it and touching to indicate when a developing hazard is visible in the clip.
If you have no sound in the above two states, first check the obvious - that your device is note muted and that the volume is not turned to zero.
One ccuser with an iPad Pro found that they didn't have sound in the above states even after double checking the obvious reasons - they resolved the issue by resetting iPad Pro.