I asked. Noise Cancel is a Gold level (I guess that means rare?) ability that you can get and can equip on any Big Band. So it's one of those icons you have on the side that you tap to use it, and it has cooldown after the attempt. I suppose a successful parry leaves them open...I wonder if you can tap it during superflashes or post-superflash.
I would assume Hidden Variable will have a system to report things, because I'll bet money they don't want to comb through a thread on some forum.
::cries to himself::