Conlon Stephen C, Fahnline John B, Semperlotti Fabio
Applied Research Laboratory, The Pennsylvania State University, University Park, Pennsylvania 16802.
Department of Aerospace and Mechanical Engineering, University of Notre Dame, Notre Dame, Indiana 46556.
J Acoust Soc Am. 2015 Jan;137(1):447-57. doi: 10.1121/1.4904501.
The concept of an Acoustic Black Hole (ABH) has been developed and exploited as an approach for passively attenuating structural vibration. The basic principle of the ABH relies on proper tailoring of the structure geometrical properties in order to produce a gradual reduction of the flexural wave speed, theoretically approaching zero. For practical systems the idealized "zero" wave speed condition cannot be achieved so the structural areas of low wave speed are treated with surface damping layers to allow the ABH to approach the idealized dissipation level. In this work, an investigation was conducted to assess the effects that distributions of ABHs embedded in plate-like structures have on both vibration and structure radiated sound, focusing on characterizing and improving low frequency performance. Finite Element and Boundary Element models were used to assess the vibration response and radiated sound power performance of several plate configurations, comparing baseline uniform plates with embedded periodic ABH designs. The computed modal loss factors showed the importance of the ABH unit cell low order modes in the overall vibration reduction effectiveness of the embedded ABH plates at low frequencies where the free plate bending wavelengths are longer than the scale of the ABH.
声学黑洞（ABH）的概念已被提出并应用于被动衰减结构振动。声学黑洞的基本原理是通过合理调整结构的几何特性，使弯曲波速逐渐降低，理论上趋近于零。对于实际系统，无法实现理想化的“零”波速条件，因此需要在低波速结构区域设置表面阻尼层，以使声学黑洞接近理想化的耗散水平。在这项工作中，开展了一项研究，以评估嵌入板状结构中的声学黑洞分布对振动和结构辐射声的影响，重点是表征和改善低频性能。使用有限元和边界元模型评估了几种板配置的振动响应和辐射声功率性能，将基线均匀板与嵌入周期性声学黑洞设计进行了比较。计算得到的模态损耗因子表明，在自由板弯曲波长大于声学黑洞尺寸的低频区域，声学黑洞单元胞低阶模态对于嵌入声学黑洞板的整体减振效果具有重要意义。
