Whether it is or not, unless he can get Cain's helmet off and then use the exact same frequency the futuristic, hyper-adaptable super sentinel used, then it doesn't really matter. That's like seeing someone get burned by Ghost Riders hellfire and only hellfire and assuming that Human Torch would be effective against them because he also uses fire.
So if he's got Nimrod's number lying around somewhere and he can call and ask, maybe he's got a shot. And that's if it even works anymore, as telepathy doesn't after his upgrade.
After this I think I need to restrict myself, at least where Juggernaut is concerned, to scenario matches. Too divorced from anything resembling reality otherwise. With it, though, good and engaging discussions can be had and all but the most resistant fans can be made to use good reasoning instead of no-limit fallacies:
http://www.killermovies.com/forums/showthread.php?threadid=602252&pagenumber=1
In no particular order:
-- Classic Juggernaut is demonstrably vulnerable to sonics.
Nimrod, sentinel from the future, put Juggernaut down with them even while fighting the X-Men. Rogue, inspired by an idea from Kitty, is the one who salvaged the fight. Note that the sonics affected Jug even though he had on a secondary helmet, proven in Marvel Team Up #150 to block psionic assault.
Several pages later ...
-- Jokester though he is, DarkSaint is right: Karnak has the ability to detect patterns and/or flaws not only in solid material, but also in force fields and sound waves.
-- Black Bolt can get impressively loud at times, almost certainly louder than Nimrod needed to get to secure the KO on Juggs.
