Low-frequency narrow-band acoustic filter with large orifice

Conventional means of attenuating airborne sound usually require blocking the air medium with a solid material. By exploiting properties of membrane-type acoustic metamaterials (MAMs), we demonstrate large transmission loss to be achievable across a sizable orifice through which air can freely flow. We find that interaction of resonating field of the MAMs with the continuous sound field passing through the orifice is responsible for such phenomenon. The narrow-band characteristic of this effect can be used for acoustic filtering of noise with a particular narrow frequency band. (C) 2013 AIP Publishing LLC.