Ultra-open acoustic metamaterial silencer

• Published in: The Journal of the Acoustical Society of America 2019-03, Vol.145 (3), p.1726-1726
• Main Authors: Ghaffarivardavagh, Reza, Nikolajczyk, Jacob, Anderson, Stephan, Zhang, Xin
• Format: Article
• Language: English
• ISSN: 0001-4966; 1520-8524
• DOI: 10.1121/1.5101343

Recently, with advances in acoustic metamaterial science, the possibility of sound attenuation using subwavelength structures, while maintaining permeability to air, has been demonstrated. However, the ongoing challenge addressed herein is the fact that among such air-permeable structures to date, the open areas represents only small fraction of the overall area of the material. In the presented work, in order to address this challenge, we firstly demonstrate that a transversely-placed bilayer medium with large degrees of contrast in the layers' acoustic properties exhibits an asymmetric transmission, similar to the Fano-like interference phenomenon. Next, we utilize this design methodology and propose a deep-subwavelength acoustic metasurface unit cell comprising nearly 60% open area for air passage, while serving as a high-performance selective sound silencer. Finally, the proposed unit cell performance is validated experimentally, demonstrating a reduction in the transmitted acoustic energy of up to 94%. This ultra-open metamaterial (UOM) design, leveraging a Fano-like interference, enables high-performance sound silencing in a design featuring a large degree of open area, which may find utility in applications in which highly efficient, air-permeable sound silencers are required, such as smart sound barriers, fan or engine noise reduction, among others.