They are starting to use that technology in diesel trucks, I believe. Imagine 2 identical tuning forks: Strike them both and they will resonate together and their volume will rise and fall rythmically depending how close they are in pitch. If you look at it on a oscilloscope, the wave pattern would look like perfect "infinity" signs end to end when the sound is muted (cancelled), and a regular sinusoidal(?) when its loudest. But if it is nerve damage, the destructive interference would still have to be picked up by your silia in the ear attached to the same damaged nerve endings? Good luck, I launched my M-47 Shoulder fired anti tank missile without ear plugs once, and they rang for about 2 days, but thank goodness, it went away.