Well -- who is "that guy"? And what's that particular youtube vid (linked in image of the pic) entitled?
Would it be too much to ask for that sort of information be included?
Is the video restricted to discussion of sound? Could there be other reasonable explanation for what the image is said to represent?
What recording is the posted image supposedly relying upon?
Who recorded it? Where was the microphone? (next to a hard wall? how far away from substantial enough in size sound reflective that could be recording small echoes?)
Could the microphone (wherever it was located -- we'll assume at some distance) have been picking up more than one sound, even from the same weapon firing? (the crack of a bullet breaking the sound barrier + the later arriving sounds of the detonation of the gun-powder coming out of the barrel and out of the action slightly out-of-sync, but those near together far more out of sync with the travel of the bullet itself breaking the sound barrier as it went zooming along, etc.)
my apologies. But maybe you can easily enough decipher what I intended to mean...
The "sound reflective" material (a wall, or anything hard and flat enough, and of enough size, and angled just so) would not itself be recording any sound, but instead, (possibly) only reflecting it towards a microphone.
Maybe all of the nonsense you posted is irrelevant. Maybe you are looking to find ANY reason to discredit a VERY CREDIBLE report by a very smart guy.
I KNOW! Maybe it was just firecrackers. /s