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. 2018 Dec 13;9:5299. doi: 10.1038/s41467-018-07809-3

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© The Author(s) 2018

Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/.

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Fig. 3 — Experimental setup and performance. a A speaker placed on the edge of a two-dimensional acoustic waveguide sends acoustic waves inside the waveguide towards a polycarbonate wall 6 mm thick. The bianisotropic metasurface replaces a wall section 17.5 cm long in the middle of the wall. The sound pressure distribution is measured in a 110 cm by 50 cm region placed immediately behind the wall. The region shows the measured sound pressure level at 3000 Hz obtained with the activated metasurface. Point A is situated 10 cm behind the metasurface. b The metasurface is composed of five meta-atoms placed side by side. Each meta-atom simulates a monopole-to-dipole inclusion embedded into the polycarbonate wall. c Photo of metasurface and wall. The monopole-to-dipole meta-atom is highlighted. d Sound pressure level (SPL) measured at 3000 Hz with the bianisotropic response activated (α_md ≠ 0) and e deactivated (α_md = 0). f SPL difference between the activated and deactivated states. The sound suppression level (SSL) is defined as the difference between the average SSLs computed in regions A and B. g Numerically simulated SPL difference for an infinitely stiff and dense wall