Ah, I see. That would be a red flag for me too. It did strike me as an odd (although very clever) solution.
Another approach I’ve seen work is what the AACA guys did. They got a sound projector and hooked it up to a sound capture device connected to a PC. Then they had to manually sync the sound file with the Kinograph image sequence in editing software. A few extra steps but definitely within your budget (until the v2 of Kinograph is finished 
)