Characterization of Membrane-Type Acoustic Metamaterial Unit Cells Fabricated by Additive Manufacturing Methods

Abstract

Membrane-type acoustic metamaterials fall into the category of metamaterials with locally resonant behavior. Adjusting the unit cell properties brings the opportunity to tune resonance/anti-resonance frequencies. Moreover, noise attenuation might be achieved in the desired frequency range using artificially engineered lightweight structures. Conventional methods for the realization of membrane-type acoustic metamaterials cause such uncertainties on the fundamental parameters: positioning and shape limitation of the masses and adjustment of membrane pre-stress. Subsequently, those methods are time-consuming considering large-scale structure fabrication. Additive manufacturing approaches minimize the side effects caused by conventional methods with a repeatable and robust process. In this research, various membrane-type acoustic metamaterial unit cells are manufactured using multimaterial printing via the fused deposition modeling (FDM) method. Flexible (TPU) filament is used for the membrane, while relatively rigid filament (PETG) is chosen for the frame and the masses. Initially, the unloaded unit cells are examined in order to evaluate 3-D printed membrane prestress and repeatability of the fabrication approach. Afterwards, the effects of membrane and mass properties on the sound transmission loss (STL) behaviors of the unit cells are investigated using an impedance tube in order to implement in multi-celled membrane-type acoustic metamaterials.