Force field nonlinear coupling and force/energy optimization in a field-induced system

Applied Physics Letters, Volume 118, Issue 18, May 2021. In a simple harmonic vibration experiment, the amplitude and energy of the vibrating object rely on the excitation field strength that determine the evolution of the vibration system. For some specific applications, such as an audio loudspeaker, in order to improve its efficiency, how to generate optimal output by applying a small exciting field to the vibration diaphragm is a big challenge for researchers. To address the difficulties, a hybrid coupling field system that consists of a coupling between static and dynamic magnetic fields is proposed in this report. In our experiment, a flexible magnetic diaphragm fabricated with the magnetic particles and polydimethylsiloxane composite is used for demonstration, where the diaphragm sandwiched between two coils generates the harmonic vibration once an external audio signal is applied, and a great enhancement of vibration can be observed when an additional magnet array is placed close to the coils. We find that the amplification of output energy is attributed to the nonlinear coupling between the static and dynamic magnetic fields excited by the magnets and currents in coils, respectively. Another interesting phenomenon resulting from the coupling is that the magnets are able to improve the audio quality, leading to a much better frequency response, which may explore some potential applications for spectrum management and acoustic metamaterials.