Membrane-ring acoustic metamaterials with an orifice

This work proposes a modified acoustic metamaterial consisting of a membrane-ring structure and orifice. Addition of the orifice can create an extra transmission loss (TL) peak besides the one originated from the membrane-ring structure. Effective mass density and phase change at their characteristic frequencies are plotted to explain responsible physical mechanisms. Capabilities of tailoring these frequencies are also exhibited. When the proposed metamaterial is backed by a cavity containing air, it is even able to serve as a ventilated composite resonator outperforming conventional ones at low frequency regimes. Different mechanisms responsible for each TL peak are identified and clearly illustrated with air velocity profiles.