Laboratoire d'Acoustique de l'Université du Maine, UMR6613 CNRS/Université du Maine, Avenue Olivier Messiaen, F-72085 Le Mans Cedex 9, France.
J Acoust Soc Am. 2011 Dec;130(6):3771-80. doi: 10.1121/1.3652865.
The acoustic properties of a porous sheet of medium static air flow resistivity (around 10,000 N m s(-4)), in which a periodic set of circular inclusions is embedded and which is backed by a rigid plate, are investigated. The inclusions and porous skeleton are assumed motionless. Such a structure behaves like a multi-component diffraction grating. Numerical results show that this structure presents a quasi-total (close to unity) absorption peak below the quarter-wavelength resonance of the porous sheet in absence of inclusions. This result is explained by the excitation of a complex trapped mode. When more than one inclusion per spatial period is considered, additional quasi-total absorption peaks are observed. The numerical results, as calculated with the help of the mode-matching method described in this paper, agree with those calculated using a finite element method.
研究了中静态空气流动阻力（约 10000 N m s(-4))的多孔薄片的声学特性，其中嵌入了周期性的圆形夹杂物，并且背面有一个刚性板。夹杂物和多孔骨架被假设为静止的。这种结构的行为类似于多分量衍射光栅。数值结果表明，在不存在夹杂物的情况下，这种结构在多孔片的四分之一波长共振以下呈现出近乎完全（接近 1）的吸收峰。这一结果可以通过激励复杂的陷波模式来解释。当每个空间周期考虑多个夹杂物时，观察到额外的准完全吸收峰。借助本文所述的模式匹配方法计算的数值结果与使用有限元方法计算的结果相吻合。
