Effective impedance boundary optimization and its contribution to dipole radiation and radiation pattern control

Abstract

Radiation pattern control has generated much interest recently due to its potential applications. Here we report the observation of high-efficiency dipole-like radiation of sound with broad bandwidth through a decorated plate with periodical two-dimensional Helmholtz resonators on both sides and a single slit at the centre. The decorated plate was optimally designed to adjust the effective impedance of the boundary, and the underlying mechanism of radiation pattern control is attributed to wave vector tailoring. The high radiation efficiency is due to the Fabry-Perot resonances associated with waveguide modes in the centre slit. The method to obtain a collimated beam without any sidelobes is also provided. Our findings should have an impact on acoustic applications.

Highly asymmetric interaction forces induced by acoustic waves in coupled plate structures

“…In recent decades, various manipulations of sound fields have been realized by tailoring artificial structures, e.g. negative refraction [10][11][12], directional radiation [13][14][15][16], and wavefront reshaping [17][18][19]. The exotic sound fields, in turn, could be used to produce abnormal ARFs.…”

Focusing and directional beaming effects of airborne sound through a planar lens with zigzag slits

“…In Fig. 3(b) we present the measured sound field distribution, which previous works, the highly directional sound beaming effect has been realized with using sonic crystals [30][31][32][33][34] and grating structures [35][36][37][38][39]. The former is frequently accompanied with the excitation of specific states in the crystals, e.g.…”

Concentric artificial impedance surface for directional sound beamforming

“…4 In addition, the concept of artificial impedance surfaces can be applied to acoustics by utilizing acoustic metasurfaces. [5][6][7][8][9][10][11][12] For example, a periodic array of Helmholtz resonators can be used to manipulate the reflection phase of incident sound waves. 6,7,10,11 In contrast to highimpedance electromagnetic surfaces, these resonant surfaces are regarded as series LC resonators.…”