title: Directional Reflective Surface Formed via Gradient-Impeding Acoustic Meta-Surfaces.
abstract: 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.
authors: Department of Nanoconvergence Systems, Korea Institute of Machinery and Materials, 156 Gajeongbuk-Ro, Daejeon, 305-343, Republic of Korea.
authors: Kyungjun
authors: K
authors: Song
authors: Department of Mechanical System Design Engineering, Hongik Univ. 94 Wausan-ro, Mapo-gu, Seoul 121-791, Seoul, Republic of Korea.
authors: Jedo
authors: J
authors: Kim
authors: Department of Nanoconvergence Systems, Korea Institute of Machinery and Materials, 156 Gajeongbuk-Ro, Daejeon, 305-343, Republic of Korea.
authors: Shin
authors: S
authors: Hur
authors: Department of Nanoconvergence Systems, Korea Institute of Machinery and Materials, 156 Gajeongbuk-Ro, Daejeon, 305-343, Republic of Korea.
authors: Jun-Hyuk
authors: JH
authors: Kwak
authors: Department of System Dynamics, Korea Institute of Machinery and Materials, 156 Gajeongbuk-Ro, Daejoen, 305-343, Republic of Korea.
authors: Seong-Hyun
authors: SH
authors: Lee
authors: Department of Mechanical Engineering, Ulsan National Institute of Science and Technology (UNIST), 50 UNIST-gil, Ulsan 44919,, Republic of Korea.
authors: Taesung
authors: T
authors: Kim
mesh_terms: D000161:Acoustic Stimulation; D000162:Acoustics / Q000295:instrumentation*; D000465:Algorithms; D006801:Humans; D008962:Models, Theoretical; D012815:Signal Processing, Computer-Assisted; D013016:Sound; D013017:Sound Localization; D013018:Sound Spectrography / Q000295:instrumentation* / Q000379:methods