Magnetorheological elastomer panels with reconfigurable magnetic mass for acoustic wave absorption

Abstract

Lightweight metamaterials based elastomeric panels are used for sound absorption of low-frequency noise. It is beneficial to tune the resonant frequency of the metamaterial, by varying the stiffness of the panel, to enable use over a broader frequency range. The stiffness of magnetorehological elastomeric (MRE) panels, composed of iron particles embedded in a PDMS matrix, can be tuned by exposure to a magnetic field. This work represents an experimental realization and theoretical understanding of a magnetic mass decorated MRE metamaterial, which allows for tunable stiffness and easy reconfiguration of the masses applied to the panel. The circular panels are clamped at the rim, outfitted with neodymium magnets, and installed in an acoustic impedance tube, where they act as an acoustic barrier between the transmit and receive sides of the tube. There are three competing mechanisms that affect the sound transmission across the panel: (1) the mass increase associated with the magnetic masses, (2) the stiffening of the panel due to the magnetic field of each mass, and (3) the increased reflection from the placed masses. The experimental results demonstrate significant sound absorption by a thin metamaterial panel over a large frequency range through careful placement of magnetic masses.