Investigation of the acoustic black hole termination for sound waves propagating in cylindrical waveguides
Investigation of the acoustic black hole termination for sound waves propagating in cylindrical waveguides
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发表时间：
2015
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通讯作者：
A. Ouahabi;V. Krylov;D. O'Boy
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作者：
A. Ouahabi;V. Krylov;D. O'Boy
到目前为止，声学黑洞主要针对薄板中的弯曲波进行研究，通过改变板的局部厚度，可以轻松实现所需的波速随距离的线性或高阶降低。本文描述了声学黑洞在空气中吸声的实验研究结果。为了实现所需的声速随传播距离的幂律减小，由 Mironov 和 Pislyakov (2002) 早期提出并由准周期肋状结构制成的非均匀声波导已被制造出来，以提供声波速度随距离的线性和二次减小。入射到黑洞的引导声波模式的反射系数的测量是在 100-1000 Hz 的频率范围内进行的。初始测量是在没有插入任何吸收材料的情况下进行的。结果表明在这种情况下可以显着减少声反射。添加小块吸收性多孔材料导致反射系数进一步降低，尽管没有预期的那么显着。
So far, acoustic black holes have been investigated mainly for flexural waves in thin plates for which the required linear or higher order reduction in wave velocity with distance can be easily achieved by changing the plate’s local thickness. In the present paper, the results of the experimental investigations of the acoustic black hole for sound absorption in air are described. To achieve the required power-law decrease in sound velocity with propagation distance the inhomogeneous acoustic waveguides earlier proposed by Mironov and Pislyakov (2002) and made of quasi-periodic ribbed structures have been manufactured to provide linear and quadratic decreases in acoustic wave velocity with distance. Measurements of the reflection coefficients for guided acoustic modes incident on the black holes have been carried out in the frequency range of 100-1000 Hz. Initial measurements were conducted without insertion of any absorbing materials. The results show the possibility of significant reduction of the acoustic reflection in this case. Addition of small pieces of absorbing porous materials caused further reduction in the reflection coefficients, albeit not as significant as it could be expected.