Slow Sound and Critical Coupling to Design Deep Subwavelength Acoustic Metamaterials for Perfect Absorption and Efficient Diffusion

Abstract

Acoustic metamaterials have recently revolutionized the field of acoustics and mechanics due to their extraordinary functionalities giving rise to breakthroughs in the material design strategy. This chapter discusses two types of acoustic metamaterial, both based on slow sound and critical coupling conditions, showing efficient absorption and diffusion at low frequencies with a deep subwavelength size. In both cases, the system will consist of a 2D flat panel composed of a periodic distribution of slits loaded by a finite array of Helmholtz resonator. By exploiting the slow sound effect, the resonance frequencies of the system can be shifted down to the low frequency range and the phase shift of the reflection coefficient can be perfectly tuned. On the contrary, the critical coupling conditions are introduced to achieve a perfect impedance matching allowing perfect absorption conditions. The chapter shows in detail both an ultra-thin absorber and ultra-thin diffusers both working in the low frequency regime.

@inbook{Romero2019,
 address = {Hoboken, NJ, USA},
 author = {Vicente Romero-García and Noé Jiménez and Jean-Philippe Groby},
 chapter = {Slow Sound and Critical Coupling to Design Deep Subwavelength Acoustic Metamaterials for Perfect Absorption and Efficient Diffusion},
 doi = {https://doi.org/10.1002/9781119649182.ch3},
 editor = {Vicente Romero-García and Anne-Christine Hladky-Hennion},
 isbn = {978-1-119-64918-2},
 pages = {47-72},
 publisher = {John Wiley \& Sons, Ltd},
 title = {Fundamentals and Applications of Acoustic Metamaterials: From Seismic to Radio Frequency},
 url = {https://onlinelibrary.wiley.com/doi/abs/10.1002/9781119649182.ch3},
 volume = {1},
 year = {2019}
}