Abstract
The technique of sound insulation has a wide range of potential applications in environment noise control and architectural acoustics. The rapid development of acoustic artificial materials has provided alternative solutions to design sound insulation structures. However, the realization of single-layer planar structures with bidirectional acoustic insulation (BAI) and unidirectional acoustic insulation (UAI) still poses a challenge. Here, we report the theoretical and experimental realization of two types of single-layer phased array lenses which presents the characteristics of broadband BAI and multi-channel UAI. Both types of lenses consist of 12 mode-conversion phased units which are composed of two types of unit cells (I and II) with an opposite phase and a step waveguide. Based on the phase regulation, the designed phased unit can realize the mode conversion between the zero-order and first-order waves and asymmetric sound manipulation, which enables multi-functional sound insulations. Based on the desired theoretical phase profiles, two types of lenses with BAI and UAI are realized for the incidence of the zero-order wave, and their fractional bandwidths can reach about 0.28 and 0.37, respectively. More interestingly, the UAI effect can be reversed for the incidence of the first-order wave. The proposed lenses based on the mode-conversion phased units have the advantages of single-layer planar structure, multi-functional sound insulation, and broad bandwidth, which have wide application prospect.
Highlights
The technique of sound insulation has attracted more and more attentions from both physics and engineering communities due to its wide potential applications in environment noise control and architectural acoustics
Including sound gratings with diffraction mechanism (Li et al, 2011; He et al, 2011; Li et al, 2014; Sun et al, 2015; Zhang et al, 2016), sonic crystals with band gap property (Li et al, 2011; Huang et al, 2016; Oh et al, 2012; Yuan et al, 2012), and nearzero-index metamaterials with abnormal refraction (Li et al, 2013; Shen et al, 2016; Song et al, 2017), and so on. In addition to these structures, acoustic metasurfaces (Li et al, 2013; Xie et al, 2014; Tang et al, 2014; Mei and Wu, 2014; Tian et al, 2017; Assouar et al, 2018; Tian et al, 2019; Quan and Alù, 2019; Holloway et al, 2019; Allen et al, 2020) provide rich possibilities to design advanced structures of sound insulation owing to its characteristics of planar structure and subwavelength thickness
We experimentally demonstrate two types of single-layer phased array lenses composed of 12 modeconversion phased units with the characteristics of broadband bidirectional acoustic insulation (BAI) and multi-channel unidirectional acoustic insulation (UAI), in which each phased unit is composed of two types of unit cells (I and II) with an opposite phase and a step waveguide
Summary
The technique of sound insulation has attracted more and more attentions from both physics and engineering communities due to its wide potential applications in environment noise control and architectural acoustics. We deduce that the broadband characteristic of the proposed phased unit arises from the stable phase difference of both types of unit cells around 7.1 kHz. for the incidence of the first-order wave (Figures 2G,H), the characteristics of the mode conversion and sound transmission created by the phased unit are opposite to those for the incidence of the zero-order wave (Figures 2A,B). The simulated pressure distributions under the incidence of the first-order wave for LI and RI match well with the corresponding propagation paths shown in Figures 2G,H, showing the characteristic of the reversed AAM based on the incidence of the first-order wave. Compared with other types of sound insulation lenses based on the phase modulation (Song et al, 2016; Zhao et al, 2017; Yu et al, 2019), the proposed lenses have the typical advantages of single-layer planar structure, multi-functional sound insulation, and broad bandwidth
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