Fire
Arm Pendulum Parametric Drive
Stand or sit, and let one arm hang. Find the minimum push that maintains amplitude indefinitely, then find the push timing that requires the largest force to achieve the same amplitude.
Full Lesson Notes
Complete Practice
Stand or sit, and let one arm hang. Initiate a very small pendular swing at the shoulder, just enough to be visible. Now, every few cycles, give a very small additional push exactly at the moment the arm is at its highest forward point. Find the minimum push that maintains amplitude indefinitely, then find the push timing that requires the largest force to achieve the same amplitude. The ratio between best and worst timing is your phase sensitivity. Challenge: Finding the exactly-highest forward point by feel is harder than the text implies; a phase error of even 50 ms changes the result.
