A spring wave has the same spirit as the pendulum wave. In this simulation, each ball oscillates back and forth on its own spring (the springs are not shown), experiencing simple harmonic motion. The frequency of the top ball is the largest, and then the frequencies decrease appropriately as you go down the screen. This could be accomplished either by increasing the masses of the balls or by decreasing the spring constant, as you go down the screen. The pattern repeats once the timer reaches 30 seconds.