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<p>Reflection invariance is a very important property in the control and manipulation of sound waves in several practical applications; however, this aspect is modestly explored in acoustic metamaterials with labyrinthine cavities. In this work, we report theoretically and experimentally a comprehensive control of sound energy by a novel subwavelength scale metamaterial based on a mirror symmetric and reciprocal labyrinth with a slit-type main pore for forward and backward incident waves. The experimental results of the sound transmission problem showed an effective attenuation greater than 22&#xa0;dB between 659 and 1495&#xa0;Hz and greater than 26&#xa0;dB between 1975 and 2750&#xa0;Hz, and this result is due to the bandgap property of local scattering and Bragg scattering of the symmetric structure. Furthermore, the results of the reflection problem showed a non-suppressible sound energy control of approximately 0.5 for the symmetric and antisymmetric modes of the structure, which allowed to reach a ratio of <InlineEquation ID="IEq1"> <EquationSource Format="TEX">\(\lambda /18\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi>λ</mi> <mo stretchy="false">/</mo> <mn>18</mn> </mrow> </math></EquationSource> </InlineEquation>. Nevertheless, due to the dispersion relation and the accumulation of absorption peaks below the bandgap, degenerate resonances were obtained in the structure and, consequently, a quasi-perfect sound absorption was obtained. The physical origin of the degenerate resonances was best understood in terms of the behavior of the acoustic pressure and the velocity of the particles in the structure. In addition, the manipulation of sound waves was experimentally evaluated by the behavior of the Bloch spatial frequency components and the phase velocity. Finally, this work contributes to advances in the area of control and manipulation of sound waves through the use of metamaterials with reflection invariance at subwavelength scale.</p>

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Control and manipulation of sound waves by a mirror symmetric reciprocal labyrinth

  • 期刊论文

  • 发表日期：

    2025年10月3日

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  • Gildean do N. Almeida,
  • Erasmo F. Vergara,
  • Arcanjo Lenzi,
  • Alosio N. Klein

摘要

Reflection invariance is a very important property in the control and manipulation of sound waves in several practical applications; however, this aspect is modestly explored in acoustic metamaterials with labyrinthine cavities. In this work, we report theoretically and experimentally a comprehensive control of sound energy by a novel subwavelength scale metamaterial based on a mirror symmetric and reciprocal labyrinth with a slit-type main pore for forward and backward incident waves. The experimental results of the sound transmission problem showed an effective attenuation greater than 22 dB between 659 and 1495 Hz and greater than 26 dB between 1975 and 2750 Hz, and this result is due to the bandgap property of local scattering and Bragg scattering of the symmetric structure. Furthermore, the results of the reflection problem showed a non-suppressible sound energy control of approximately 0.5 for the symmetric and antisymmetric modes of the structure, which allowed to reach a ratio of \(\lambda /18\) λ / 18 . Nevertheless, due to the dispersion relation and the accumulation of absorption peaks below the bandgap, degenerate resonances were obtained in the structure and, consequently, a quasi-perfect sound absorption was obtained. The physical origin of the degenerate resonances was best understood in terms of the behavior of the acoustic pressure and the velocity of the particles in the structure. In addition, the manipulation of sound waves was experimentally evaluated by the behavior of the Bloch spatial frequency components and the phase velocity. Finally, this work contributes to advances in the area of control and manipulation of sound waves through the use of metamaterials with reflection invariance at subwavelength scale.