As a musician working occasionally with audio, I've long wondered about tremor frequency and the phenomenon known as phase cancellation. If you take two audio signals of identical frequency and have them occur 180 degrees out of phase with each other, they cancel out the sound. It's how some noise cancellation headphones operate. So if say a parkinson's tremor happens at 4 hz, could one theoretically set up a device that would fire at 4 hz but would be out of phase and thus eliminate the noisy shaking?

Jon