Self-driven oscillators with wave-feedback forcing resist analytic prediction

Evidence

What makes the system nonlinear is that, instead of a prescribed forcing function like F(t) = F0 sin(2π ft), the drive force depends on the amplitude of the wave at a specific point—the float. The arrival of crests and troughs affects when the valve opens and closes. Predicting the shape that the wave takes after many periods (knowing the amplitude and phases of each of the partials) is difficult, a task fit for computers. — Eric J. Heller, Why You Hear What You Hear- An…, 1549

Categorization

• DEFINE: Characterizes what makes a wind instrument’s drive nonlinear: forcing depends on wave amplitude at a point, not an externally prescribed function.