04.snap-detector-refactor-01.improving-the-target-detection.mp4 , sound in the beginning and the sound stops at 00:36
04.snap-detector-refactor-02.hooking-onto-any-surface.mp4 , no sound at all
04.snap-detector-refactor-03.visualizing-the-hooking-range.mp4 , no sound at all
The videos following seem to have sound, I've not watched them all yet.
I've tested this both on my tablet and desktop computer, so it's not a mediaplayer problem, and there's sound on the online versions on this page.