The appearance of higher amplitude sound waves could seem, at first, like a path to net gain. Dicke "superradiance is involved as well as Fermi-Pasta-Ulam
https://en.wikipedia.org/wiki/Fermi%E2%80%93Pasta%E2%80%93Ulam%E2%80%93Tsingou_problem H LV wrote: Acoustic demonstration of beats https://www.youtube.com/watch?v=IYeV2Wq82fw This is not mentioned in the video but beats also arise and persist in a driven oscillator when no damping force is present. This happens because the driver`s frequency does not match the natural frequency of the oscillator. Beats will also initially appear in a driven oscillator when a damping force is present but they will fade away quickly. Harry
