ELFT HÍRADÓ

[mcsete AT physx.u-szeged.hu]

Seminar

Speaker: Professor Oliver B. Wright
Graduate School of Engineering, Osaka University
& Hokkaido University, Sapporo

Date: 3pm, 17, April (Wednesday) 2024
Location: SZTE TTIK FI, Budó auditorium & online
https://join.skype.com/MUc2Kch694Wk

Title: Coaxing sound through small apertures with metamaterials

Abstract: Acoustic metamaterials are non-naturally occurring  
structures consisting of arrangements of sub-wavelength resonators  
designed to manipulate the propagation of sound. After presenting the  
basics of this subject, I will present several examples of  
metamaterial-enabled acoustic extraordinary transmission, that is,  
enhanced acoustic transmission through small holes or structures,  
namely, enhanced transmission of membrane covered holes, from water to  
air, of surface acoustic waves on solids and of sound transmission  
through small rods. Finally, I will discuss the curious case of  
enhanced transmission through bare holes without resonance using the  
language of metamaterials.

Electromagnetic metamaterials, consisting of sub-wavelength  
oscillators that show effective negative permeability or permittivity  
have led to many applications over the last 20 years. In parallel,  
acoustic metamaterials showing effective negative density or modulus  
were introduced [1,2]. Curious phenomena such as acoustic negative  
refraction, superlensing and cloaking were demonstrated. Here I will  
present and review the topic of metamaterial-based extraordinary  
acoustic transmission, i.e., the passage of more acoustic energy than  
expected through small sub-acoustic-wavelength apertures.

I will first present our experimental work in this field using kHz  
airborne acoustics [3], for which giant transmission was demonstrated,  
and also simulations in solid acoustics of surface or bulk waves  
[4-5]. Closely related to extraordinary acoustic transmission is the  
phenomenon of enhanced transmission between acoustically mismatched  
media. I will also review experimental work on the enormously enhanced  
passage of acoustic waves from water to air based on the use of a kHz  
acoustic metasurface [6].

Finally, I will present very recent kHz experiments on the  
transmission of airborne sound through bare holes without the  
occurrence of any resonance [7]. Although resonances are essential in  
optics to overcome poor transmission through bare holes, this is not  
so in fluid acoustics. A plate perforated with bare holes can transmit  
nearly all the sound normally incident on it, which has practical  
applications in sound transparent screens. However, this phenomenon  
has not previously been systematically interpreted in terms of  
extraordinary transmission. I will present such an analysis, and hope  
to make you appreciate how sound-transparent screens with holes at  
bank service counters work, and how to optimize them.

[1] Z. Liu, X. Zhang, Y. Mao, Y. Zhu, Z. Yang, C. T. Chan, and P.  
Sheng, Science 289, 1734 (2000).
[2] S. H. Lee and O. B. Wright, Phys. Rev. B 93, 024302 (2016).
[3] J. J. Park, K. J. B. Lee, O. B. Wright, M. K. Jung, and S. H. Lee,  
Phys. Rev. Lett. 110, 244302 (2013).
[4] S. Mezil, K. Chonan, P. H. Otsuka, M.Tomoda, O. Matsuda, S. H.  
Lee, and O. B. Wright, Sci. Rep. 6, 33380 (2016).
[5] T. Devaux, H. Tozawa, P. H. Otsuka, S. Mezil, M. Tomoda, O.  
Matsuda, E. Bok, S. H. Lee, and O. B. Wright, Sci. Adv. 6, 8507 (2020)
[6] E. Bok, J. J. Park, H. Choi, C. K. Han, O. B. Wright, and S. H.  
Lee, Phys. Rev. Lett. 120, 044302 (2018).
[7] E. Bok, J. J. Park, A. A. Maznev, S. H. Lee, and O. B. Wright,  
Phys. Rev. B 108, 144111 (2023)

Everyone is welcome to attend.

Dr. Mária Csete


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