双迷宫型通道Helmholtz周期结构的低频带隙机理及隔声特性

为了解决飞机舱室中的低频噪声问题,本文设计了一种双迷宫型通道的Helmholtz周期结构。迷宫型开口通道的设计能够大大增加Helmholtz腔开口通道的长度,有效降低低频带隙下限,双通道的设计能够增加声子晶体局域共振的区域,可以增加低频带隙数目。本文采用有限元法(FEM)得到了该结构在0~500 Hz频率范围内的能带结构及隔声特性,经过深入研究发现,该Helmholtz 周期结构在0~500 Hz范围内存在多个低频带隙,且在低频范围内表现出较好的隔声特性。为了揭示其带隙产生机理,本文通过声-电类比方法建立了该结构的等效电路模型,并通过有限元法和等效电路模型,对低频带隙影响因素进行了详细分析。结果表明,增加开口通道的长度能够降低带隙起始频率,较小的晶格常数有利于拓宽带隙宽度。本文的研究进一步探索了声子晶体结构设计对带隙的影响,为解决飞机舱室的低频降噪问题提供了新方法。

Low-Frequency Band Gap Mechanism and Sound Insulation Characteristics of Helmholtz Periodic Structure with Double Labyrinth Tubes

To solve the problem of low-frequency noise in aircraft cabin, a Helmholtz periodic structure with double labyrinth tubes was proposed in this paper. The design of labyrinth tubes greatly increases the length of tubes of Helmholtz resonator, reducing the lower limit of low-frequency band gap. The design of double opening tubes can increase the region of local resonance of the phononic crystal, therefore, the number of low-frequency band gaps increases. Firstly, the band structure and sound insulation characteristics of the structure in the frequency range from 0 Hz to 500 Hz were characterized by finite element method (FEM). It is found that the structure has multiple complete low-frequency band gaps in the frequency range from 0 Hz to 500 Hz, showing an excellent low-frequency sound insulation characteristic. Secondly, to reveal the mechanism of band gap, the equivalent circuit model was established by the method of electro-acoustic analogy. Finally, the influence factors of band gaps were analyzed by FEM and equivalent model. It is found that increasing the length of the tubes can effectively reduce the lower limit of the band gap, and a smaller lattice constant is beneficial to widen the band gap. The research in this paper further explores the influence of phononic crystal structure design on band gap and provides a new method for low-frequency noise reduction of aircraft cabin.