Melnikov Anton, Chiang Yan Kei, Quan Li, Oberst Sebastian, Alù Andrea, Marburg Steffen, Powell David
Vibroacoustics of Vehicles and Machines, Technical University of Munich, Garching b. Munich, 85748, Germany.
SBS Bühnentechnik GmbH, Dresden, 01259, Germany.
Nat Commun. 2019 Jul 17;10(1):3148. doi: 10.1038/s41467-019-10915-5.
Acoustic metamaterials are structures with exotic acoustic properties, with promising applications in acoustic beam steering, focusing, impedance matching, absorption and isolation. Recent work has shown that the efficiency of many acoustic metamaterials can be enhanced by controlling an additional parameter known as Willis coupling, which is analogous to bianisotropy in electromagnetic metamaterials. The magnitude of Willis coupling in a passive acoustic meta-atom has been shown theoretically to have an upper limit, however the feasibility of reaching this limit has not been experimentally investigated. Here we introduce a meta-atom with Willis coupling which closely approaches this theoretical limit, that is much simpler and less prone to thermo-viscous losses than previously reported structures. We perform two-dimensional experiments to measure the strong Willis coupling, supported by numerical calculations. Our meta-atom geometry is readily modeled analytically, enabling the strength of Willis coupling and its peak frequency to be easily controlled.
声学超材料是具有奇异声学特性的结构，在声束转向、聚焦、阻抗匹配、吸收和隔离方面有着广阔的应用前景。最近的研究表明，通过控制一个被称为威利斯耦合的额外参数，可以提高许多声学超材料的效率，这类似于电磁超材料中的双各向异性。理论上已表明，无源声学元原子中的威利斯耦合强度存在上限，但尚未通过实验研究达到这一极限的可行性。在此，我们引入了一种具有威利斯耦合的元原子，它非常接近这一理论极限，并且比先前报道的结构更简单，更不易产生热粘性损耗。我们进行了二维实验来测量强威利斯耦合，并辅以数值计算。我们的元原子几何结构易于进行解析建模，能够轻松控制威利斯耦合的强度及其峰值频率。
