Visco-thermal effects in acoustic metamaterials: from total transmission to total reflection and high absorption

• Published in: New journal of physics Vol. 18; no. 3; pp. 33003 - 33010
• Main Authors: Molerón, Miguel, Serra-Garcia, Marc, Daraio, Chiara
• Format: Journal Article
• Language: English
• Published: Bristol IOP Publishing 01-03-2016
• Subjects: Acoustic absorption; acoustic metamaterials; Acoustic propagation; Acoustics; Energy dissipation; extraordinary transmission; Fabry-Perot resonance; Metamaterials; Physics; Reflection; Slits; Temperature effects; viscous and thermal losses
• ISSN: 1367-2630; 1367-2630
• DOI: 10.1088/1367-2630/18/3/033003

We theoretically and experimentally investigate visco-thermal effects on the acoustic propagation through metamaterials consisting of rigid slabs with subwavelength slits embedded in air. We demonstrate that this unavoidable loss mechanism is not merely a refinement, but that it plays a dominant role in the actual acoustic response of the structure. Specifically, in the case of very narrow slits, the visco-thermal losses avoid completely the excitation of Fabry-Perot resonances, leading to 100% reflection. This is exactly opposite to the perfect transmission predicted in the idealised lossless case. Moreover, for a wide range of geometrical parameters, there exists an optimum slit width at which the energy dissipated in the structure can be as high as 50%. This work provides a clear evidence that visco-thermal effects are necessary to describe realistically the acoustic response of locally resonant metamaterials.