Abstract
To achieve high-efficiency acoustic focusing, an artificial periodic acoustic structure composed of two-dimensional three-component cell arrays was used to manipulate the transmission wave fronts of acoustic waves, and the acoustic field characteristics were numerically simulated by COMSOL finite element software. The results showed that whether the spherical acoustic wave generated by the point excitation source or the planar acoustic wave generated by the linear excitation source was used as the incident wave, an emission focus point can be generated at the top of the acoustic model. The intensity of the acoustic pressure at the focus point depended on the frequency of the incident acoustic waves. Under the same vibration period, the acoustic pressure will increase first and then decrease. It will reach a maximum value at the resonance frequency. In addition, when the model was cut into a right-angled trapezoidal structure with the axis of symmetry as a cross-section, the acoustic wave can produce a variable-direction focusing effect, and the “acoustic levitation” effect can also be realized. This series of anomalous acoustic phenomena can provide a new direction for acoustic directional transmission, acoustic wave detection, and acoustic stealth.
Highlights
INTRODUCTIONWith the rise of photonic crystals in the field of condensed matter physics in recent years, the use of artificial periodic structures for electromagnetic wave manipulation technology has become more and more mature. Since acoustic waves and light waves belong to the same classical wave, how to use acoustic artificial structures to achieve some anomalous acoustic characteristics that are not available in traditional acoustic materials has attracted wide attention of researchers
With the rise of photonic crystals in the field of condensed matter physics in recent years, the use of artificial periodic structures for electromagnetic wave manipulation technology has become more and more mature.1,2 Since acoustic waves and light waves belong to the same classical wave, how to use acoustic artificial structures to achieve some anomalous acoustic characteristics that are not available in traditional acoustic materials has attracted wide attention of researchers.In 2000, Liu et al.3 introduced a resonant structural system and periodically embedded it in the elastic medium matrix to realize the phononic crystal band gap
Whether the spherical acoustic wave generated by the point source or the plane acoustic wave generated by the linear source will diffuse and attenuate outward in the free plane, and the attenuation amplitude is positively correlated with the transmission distance
Summary
With the rise of photonic crystals in the field of condensed matter physics in recent years, the use of artificial periodic structures for electromagnetic wave manipulation technology has become more and more mature. Since acoustic waves and light waves belong to the same classical wave, how to use acoustic artificial structures to achieve some anomalous acoustic characteristics that are not available in traditional acoustic materials has attracted wide attention of researchers. In 2007, Dong et al. designed the two-dimensional (2D) single-phase anisotropic elastic metamaterials with broadband double-negative effective material properties and demonstrated the superlensing effect at the deepsubwavelength scale This series of research results laid the foundation for the development of acoustic artificial periodic structure and provided a new direction for manipulating acoustic waves. In 2017, Lan et al. designed a gradient acoustic metasurface based on Helmholtz Resonators to manipulate acoustic wavefront Their theoretical and numerical results showed that sub-wavelength flat focusing can be realized by adjusting the slit width of unit cell. We propose to design an acoustic focusing lens by periodically arranging two-dimensional threecomponent locally resonant units of the same size, which can achieve the acoustic focusing effect with high efficiency and reduce the difficulty of sample preparation. Our model can achieve the focusing of plane wave and spherical wave periodically in a wide frequency band, which may provide a new direction for acoustic signal detection and medical imaging
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