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1.
The transfer matrix method was used to analyze the acoustical properties of stepped acoustic resonator in the previous paper. The present paper extends the application of the transfer matrix method to analyzing acoustic resonators with gradually varying cross-sectional area. The transfer matrices and the resonant conditions are derived for acoustic resonators with four different kinds of gradually varying geometric shape: tapered, trigonometric, exponential and hyperbolic. Based on the derived transfer matrices, the acoustic properties of these resonators are derived, including the resonant frequency, phase and radiation impedance. Compared with other analytical methods based on the wave equation and boundary conditions, the transfer matrix method is simple to implement and convenient for computation.  相似文献   

2.
This paper presents a theoretical and experimental study of noise control in enclosures using a T-shaped acoustic resonator array. A general model with multiple resonators is developed to predict the acoustic performance of small resonators placed in an acoustic enclosure. Analytical solutions for the sound pressure inside the enclosure and the volume velocity source strength out of the resonator aperture are derived when a single resonator is installed, which provides insight into the physics of acoustic interaction between the enclosure and the resonator. Based on the understanding of the coupling between the individual resonators and enclosure modes, both targeted and nontargeted, a sequential design methodology is proposed for noise control in the enclosure using an array of acoustic resonators. Design examples are given to illustrate the control performance at a specific or at several resonance peaks within a frequency band of interest. Experiments are conducted to systematically validate the theory and the design method. The agreement between the theoretical and experimental results shows that, with the help of the presented theory and design methodology, either single or multiple resonance peaks of the enclosure can be successfully controlled using an optimally located acoustic resonator array.  相似文献   

3.
共焦腔是一般稳定腔的特例,由于等价性,共焦腔中自再现模的振幅分布、损耗和光斑尺寸常常被用于讨论一般稳定腔。为了分析具有大菲涅尔数的圆镜共焦腔,本文利用传输矩阵方法对腔模进行计算和讨论。研究结果表明:传输矩阵方法的结果与Fox-Li积分迭代法的结果一致,并且传输矩阵方法实用于大菲涅尔数共焦腔。  相似文献   

4.
The influence of acoustic resonators on the acoustic and propulsion performance characteristics of a ramjet ejector chamber under conditions with vibration hydrogen combustion was experimentally examined. In the study, resonators having identical throats and different cavity diameters were used. For fixed-volume resonators the best propulsion performance characteristics were achieved in the case in which the cavity diameter differed little from the resonator throat diameter.  相似文献   

5.
水下圆柱形Helmholtz共振器的声学特性分析   总被引:2,自引:0,他引:2       下载免费PDF全文
王泽锋  胡永明  孟洲  倪明 《物理学报》2008,57(11):7022-7029
理论分析了水下圆柱形Helmholtz共振器的声学特性. 综合考虑壁面弹性和辐射阻抗的影响,基于电-声类比的基本原理,建立了较为完善的水下圆柱形Helmholtz共振器的低频集中参量模型. 利用电路分析的基本方法,得到了系统的输入阻抗和声压传递函数表达式. 仿真分析了主要结构参数对共振器声学特性的影响,得出了一些有意义的结论. 在充水驻波罐中对自制的Helmholtz共振器进行了测量,并对实验结果进行了详细地误差分析. 去除压电水听器对测量结果的影响后,实验与仿真结果基本一致,从而验证了理论分析的正确性. 关键词: Helmholtz共振器 共振频率 传递函数 辐射阻抗  相似文献   

6.
Acoustic design parameters of a half-wave resonator are studied experimentally for purely acoustic tuning of the resonator. According to the standard acoustic-test procedures, acoustic-pressure signals in the model enclosure with the resonators are measured. Based on the signals, quantitative acoustic properties of damping factor and sound absorption coefficient are evaluated and thereby, the acoustic-damping capacity of the resonator is characterized. Sound absorption coefficient has the advantages of the damping factor in various aspects. The coefficient indicates clearly the tuning frequency of the resonator, absorption effectiveness as a function of frequency, and overall damping capacity. The diameter and the number of a half-wave resonator, its distribution, and the blockage ratio at its inlet are selected as design parameters for optimal tuning of the resonator in the model enclosure. The resonators with larger diameter have the advantage of those with smaller one with respect to purely acoustic damping at the tuning frequency. The optimum number of resonators or the optimum open-area ratio decreases as boundary absorption decreases. When the open-area ratio exceeds the optimum value, over-damping appears, leading to a decrease in peak absorption coefficient and a broadening of absorption bandwidth. Blockage at the resonator inlet controls both peak absorption coefficient and its absorption bandwidth and it can be considered one of design factors for acoustic tuning.  相似文献   

7.
A resonator with perforated intruding inlet (PII) is a superior silencer element, since the use of perforated inlet extensions can dramatically improve the acoustic performance. In this work, both a one-dimensional (1D) and a two-dimensional (2D) transfer matrix methods are developed to predict the transmission loss of the resonator without considering the mean flow. Based on the two groups of comparisons with tests, it is found out that the applicability of 1D method is limited by the resonator geometry even when the frequency is below the cut-off value of plane wave. Whereas the 2D approach is much more accurate while predicting the transmission losses within entire frequency range. Subsequently, five groups of resonators are chosen to determine the effects of structure parameters to transmission loss based on the 2D approach. The resonant frequency decreases and more resonant peaks appear when the length of inlet extension increases. A higher perforation rate leads to a shift of resonant peak towards higher frequencies. Besides, better acoustic performance could be obtained with the perforation being properly designed. Reducing the inlet/outlet radius can obviously improve the transmission loss without changing the frequency of resonant peak. The theories and conclusions in this study can be used for the design and optimization of resonators in various engineering applications.  相似文献   

8.
王泽锋  胡永明  熊水东  罗洪  孟洲  倪明 《物理学报》2009,58(4):2507-2512
理论和实验研究了腔壁弹性对水下小型圆柱形亥姆霍兹共振器共振频率的影响.基于电-声类比理论,建立了小型共振器的简化模型,利用电路分析方法得到了便于计算的共振频率一般表达式.分别仿真分析了共振器壁面厚度和材料对共振频率的影响,得到了不同尺寸的小型共振器的近似刚性条件.在充水驻波罐中对不同壁厚、不同材料的小型圆柱形亥姆霍兹共振器的共振频率进行了测量,实验结果较好地验证了理论分析和近似刚性条件的正确性.所得结果对小型圆柱形亥姆霍兹共振器的设计和水下应用具有较好的参考价值. 关键词: 亥姆霍兹共振器 共振频率 传递函数 辐射阻抗  相似文献   

9.
Sonic crystals can be used as acoustic lenses in certain frequencies and the design of such systems by creating vacancies and using genetic algorithms has been proven to be an effective method. So far, rigid cylinders have been used to create such acoustic lens designs. On the other hand, it has been proven that Helmholtz resonators can be used to construct acoustic lenses with higher refraction index as compared to rigid cylinders, especially in low frequencies by utilizing their local resonances. In this paper, these two concepts are combined to design acoustic lenses that are based on Helmholtz resonators. The Multi-Level Wave Based Method is used as the prediction method. The benefits of the method in the context of design procedure are demonstrated. In addition, symmetric boundary conditions are derived for more efficient calculations. The acoustic lens designs that use Helmholtz resonators are compared with the acoustic lens designs that use rigid cylinders. It is shown that using Helmholtz resonator based sonic crystals leads to better acoustic lens designs, especially at the low frequencies where the local resonances are pronounced.  相似文献   

10.
有源腔模式的有限元数值矩阵计算法   总被引:4,自引:0,他引:4  
提出了一种计算有源腔模式分布的有限元数值矩阵方法。对腔镜进行基于菲涅耳–基尔霍夫衍射积分定理的有限元划分,利用MATLAB计算出光一次往返的传输矩阵。然后根据自再现理论,求出矩阵的特征值和特征向量。从而确定谐振腔的模式分布,给新型谐振腔的研究带来极大方便。  相似文献   

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