Magnetoactive acoustic metamaterials based on nanoparticle-enhanced diaphragm

Magnetoactive membrane-type acoustic metamaterials are fabricated by coating a layer of magnetic nanoparticles on the polyethylene (PE) membranes and their vibration characters are investigated experimentally. From our experiments, we discovered that, under different magnetic fields by varying the distance between a magnet and the membranes, such membranes exhibit tunable vibration eigenfrequencies (the shift towards lower frequencies), which is caused by the variation of the effective mass density and effective tension coefficient resulted from the second derivative of the magnetic field. The strong magnetic force between the layer of magnetic nanoparticles and the magnet enhances the eigenfrequency shift. A spring oscillator model is proposed and it agrees well with the experimental results. We also experimentally observed that the vibration radius, effective mass density, and effective tension coefficient of the membranes can enormously affect the eigenfrequencies of the membranes. We believe that this type of metamaterials may open up some potential applications for acoustic devices with turntable vibration properties.

Automated summary

The study found that the vibration frequency of magnetoactive membrane-type acoustic metamaterials can be tuned by changing the magnetic field, which is caused by the variation of effective mass density and effective tension coefficient. The strong magnetic force between the layer of magnetic nanoparticles and the magnet enhances the shift in eigenfrequency of the membrane. The experimental results were in good agreement with the proposed spring oscillator model, showing the significant impact of vibration radius, effective mass density, and effective tension coefficient on the membrane's eigenfrequencies.