..He went inactive first.. >_>
But yeah, I don't think it was long after. xD
My initial response would have been that it's forcefulness was based in Fuuton's "pushing" trait, and that it was the strength of the repeated waves of chakra that created the effect, but after rethinking it, I believe it could also be attributed to Raiton's vibration trait, and that the effect of this technique comes from a drastic increase in the severity of the waves' oscillation, reaching violent enough levels to disturb objects within a certain range from the point of origin before weakening outside of mid-range. Perhaps a combination of both? If not, I think I may return to my first answer.
Hmm.. Recent applications of sound that I've seen have all been a bit tricky in the area of speed, with some claiming that sound moves too quickly to be responded to by normal means, which I doubt is/hope is not the case, or at least wont be the case for long. The labeled "counters" for Sound are Earth and Wind, with the latter being the only semi-reliable one (or so it seems to me), but, in my specific case, I would want to play it as safe as possible when dealing with Sound. With this specific technique, I would rely on my doujutsu to see the Ototon chakra being molded and preparing myself in such a way that I would either mimic the same technique or utilize another Ototon technique with the same damage basis as absolutely, microscopically close to the opponent's beginning of their technique as physically possible, resulting in a collision of the forces that would hopefully result in a mutual cancellation, or one overpowering the other, depending on technique rank/damage. If that's not possible, I'd have to see the chakra ahead of time, and try my timing with a Fuuton technique of the same rank or higher that would be large enough to protect my entire body from the sound waves and would not require handseals (as I'd need my hands free to cross my fingers.).