Directional Reflective Surface Formed via Gradient-Impeding Acoustic Meta-Surfaces

Artificially designed acoustic meta-surfaces have the ability to manipulate sound energy to an extraordinary extent. Here, we report on a new type of directional reflective surface consisting of an array of sub-wavelength Helmholtz resonators with varying internal coiled path lengths, which induce a reflection phase gradient along a planar acoustic meta-surface. The acoustically reshaped reflective surface created by the gradient-impeding meta-surface yields a distinct focal line similar to a parabolic cylinder antenna, and is used for directive sound beamforming. Focused beam steering can be also obtained by repositioning the source (or receiver) off axis, i.e., displaced from the focal line. Besides flat reflective surfaces, complex surfaces such as convex or conformal shapes may be used for sound beamforming, thus facilitating easy application in sound reinforcement systems. Therefore, directional reflective surfaces have promising applications in fields such as acoustic imaging, sonic weaponry, and underwater communication.

[1]  P. Sheng,et al.  Dark acoustic metamaterials as super absorbers for low-frequency sound , 2012, Nature Communications.

[2]  Chiara Daraio,et al.  Acoustic Fresnel lenses with extraordinary transmission , 2014 .

[3]  Acoustic guiding and subwavelength imaging with sharp bending by sonic crystal , 2011, 1108.0764.

[4]  R. Fleury,et al.  Sound Isolation and Giant Linear Nonreciprocity in a Compact Acoustic Circulator , 2014, Science.

[5]  Jennifer Urner,et al.  Antenna Theory And Design , 2016 .

[6]  D. Blackstock.  Fundamentals of Physical Acoustics , 2000 .

[7]  R. T. Beyer,et al.  Experimental Investigation of an End-Fire Array , 1962 .

[8]  D. Sievenpiper,et al.  High-impedance electromagnetic surfaces with a forbidden frequency band , 1999 .

[9]  G. Wade.  Acoustic Imaging : Cameras, Microscopes, Phased Arrays, and Holographic Systems , 1976 .

[10]  Zhengyou Liu,et al.  Highly directional acoustic wave radiation based on asymmetrical two-dimensional phononic crystal resonant cavity , 2006 .

[11]  Huanyang Chen,et al.  Wavefront modulation and subwavelength diffractive acoustics with an acoustic metasurface , 2014, Nature Communications.

[12]  Bruno Morvan,et al.  Ultra-directional source of longitudinal acoustic waves based on a two-dimensional solid/solid phononic crystal , 2014 .

[13]  Chunguang Xia,et al.  Broadband acoustic cloak for ultrasound waves. , 2010, Physical review letters.

[14]  Yong Li,et al.  Metascreen-Based Acoustic Passive Phased Array , 2015 .

[15]  Hyok J. Song,et al.  Two-dimensional beam steering using an electrically tunable impedance surface , 2003 .

[16]  Bin Liang,et al.  Three-dimensional Ultrathin Planar Lenses by Acoustic Metamaterials , 2014, Scientific Reports.

[17]  Shulin Sun,et al.  Gradient-index meta-surfaces as a bridge linking propagating waves and surface waves. , 2012, Nature materials.

[18]  Baowen Li,et al.  Manipulating Acoustic Wavefront by Inhomogeneous Impedance and Steerable Extraordinary Reflection , 2013, Scientific Reports.

[19]  Andrew G. Glen,et al.  APPL , 2001 .

[20]  Shi-ning Zhu,et al.  Acoustic surface evanescent wave and its dominant contribution to extraordinary acoustic transmission and collimation of sound. , 2010, Physical review letters.

[21]  Xiaobo Yin,et al.  A holey-structured metamaterial for acoustic deep-subwavelength imaging , 2011 .

[22]  Jensen Li,et al.  Extreme acoustic metamaterial by coiling up space. , 2012, Physical review letters.

[23]  Kyungjun Song,et al.  Sound Pressure Level Gain in an Acoustic Metamaterial Cavity , 2014, Scientific Reports.

[24]  Experimental demonstration of directional acoustic radiation based on two-dimensional phononic crystal band edge states , 2007 .

[25]  Bin Liang,et al.  Reflected wavefront manipulation based on ultrathin planar acoustic metasurfaces , 2013, Scientific Reports.

[26]  F. García-Vidal,et al.  Collimation of sound assisted by acoustic surface waves , 2007 .

[27]  Shin Hur,et al.  Emission Enhancement of Sound Emitters using an Acoustic Metamaterial Cavity , 2014, Scientific Reports.

[28]  Y. Cheng,et al.  Tunable sound directional beaming assisted by acoustic surface wave , 2010 .

[29]  Pai Peng,et al.  Flat acoustic lens by acoustic grating with curled slits , 2014 .

[30]  Xiaobo Yin,et al.  Experimental demonstration of an acoustic magnifying hyperlens. , 2009, Nature materials.

[31]  P. J. Westervelt.  Parametric Acoustic Array , 1963 .

[32]  Yong Li,et al.  Acoustic focusing by coiling up space , 2012 .

[33]  Yong Li,et al.  Experimental realization of full control of reflected waves with subwavelength acoustic metasurfaces , 2014, 1407.1138.

[34]  Zhengyou Liu,et al.  Directional acoustic source based on the resonant cavity of two-dimensional phononic crystals , 2005 .

[35]  Xiaopeng Zhao,et al.  The anomalous manipulation of acoustic waves based on planar metasurface with split hollow sphere , 2015 .

[36]  P. Johnson,et al.  Effective impedance boundary optimization and its contribution to dipole radiation and radiation pattern control , 2014, Nature Communications.

[37]  Zhengyou Liu,et al.  Acoustic directional radiation and enhancement caused by band-edge states of two-dimensional phononic crystals , 2006 .