深亚波长尺度的三维超薄声准直器件

Three-dimensional ultra-thin acoustic collimation device with deep sub-wavelength scale

文章提出了一个以空气为背景介质、具有强指向性的三维超薄人工结构。该结构包含一个中心螺旋结构,结构上下两侧刻有呈米字型排列的亥姆霍兹共振腔(Helmholtz Resonator, HR)凹槽阵列。中心螺旋结构降低了结构厚度,使整体结构厚度仅为入射波长的1/10,同时延长了声波的传播距离,实现了低频处的法布里-珀罗(Fabry-Perot,F-P)共振。两侧HR凹槽阵列将散射声波转换为束缚在结构表面的声表面波,通过声表面波和F-P共振产生的透射声波的耦合实现了声波的准直发射。仿真结果证明该准直低频声束在透射端自由声场的传播距离大于15个入射波长。该三维器件在深亚波长尺度实现了高指向性声辐射,有望广泛应用于噪声控制及电声设计等领域。

A three-dimensional ultra-thin artificial structure with strong directivity is proposed in this paper. The structure contains a central spiral structure and HR groove arrays which are engraved on the upper and lower sides of the structure. The central spiral structure reduces the thickness of the structure to make the overall structure thickness only one-tenth of the incident wavelength, extend the propagation distance of sound waves, and achieve F-P resonance at low frequencies. The HR groove arrays on both sides convert the scattered acoustic waves into surface acoustic waves bounding to the surface of the structure. The collimated emission of the acoustic waves is realized by coupling of the surface acoustic waves and the transmitted acoustic waves generated by the F-P resonance. The simulation results prove that the transmission distance of the collimated acoustic beam in the free sound field exceeds 15 times of the incident wavelength. The three-dimensional device achieves high-directional acoustic radiation in the deep sub-wavelength scale,and it is expected to have practical application values in noise control and electroacoustic design, etc.