Papadakis Nikolaos M, Stavroulakis Georgios E
Institute of Computational Mechanics and Optimization (Co.Mec.O), School of Production Engineering and Management, Technical University of Crete, 73100 Chania, Greece.
Micromachines (Basel). 2023 Oct 15;14(10):1932. doi: 10.3390/mi14101932.
One of the uses of Helmholtz resonators is as sound absorbers for room acoustic applications, especially for the low frequency range. Their efficiency is centered around their resonance frequency which mainly depends on elements of their geometry such as the resonator volume and neck dimensions. Incorporating additional necks on the body of a Helmholtz resonator (depending on whether they are open or closed) has been found to alter the resulting resonance frequency. For this study, tunable Helmholtz resonators to multiple resonance frequencies, are proposed and investigated utilizing additional necks. The resonance frequencies of various multi-neck Helmholtz resonators are first modeled with the use of the finite element method (FEM), then calculated with the use of an analytical approach and the results of the two approaches are finally compared. The results of this study show that Helmholtz resonators with multiple resonances at desired frequencies are achievable with the use of additional necks, while FEM and analytical methods can be used for the estimation of the resonance frequencies. Analytical and FEM approach results show a good agreement in cases of small number of additional necks, while the increasing differences in cases of higher neck additions, were attributed to the change in effective length of the necks as demonstrated by FEM. The proposed approach can be useful for tunable sound absorbers for room acoustics applications according to the needs of a space. Also, this approach can be applied in cases of additional tunable air resonances of acoustic instruments (e.g., string instruments).
亥姆霍兹共鸣器的用途之一是作为室内声学应用的吸声器，特别是在低频范围内。它们的效率集中在其共振频率周围，而共振频率主要取决于其几何形状的要素，如共鸣器的体积和颈部尺寸。人们发现，在亥姆霍兹共鸣器的主体上增加额外的颈部（取决于它们是开放的还是封闭的）会改变产生的共振频率。在本研究中，利用额外的颈部提出并研究了具有多个共振频率的可调谐亥姆霍兹共鸣器。首先使用有限元方法（FEM）对各种多颈部亥姆霍兹共鸣器的共振频率进行建模，然后使用解析方法进行计算，最后比较这两种方法的结果。这项研究的结果表明，通过使用额外的颈部，可以实现具有所需频率的多个共振的亥姆霍兹共鸣器，而有限元方法和解析方法可用于估计共振频率。在额外颈部数量较少的情况下，解析方法和有限元方法的结果显示出良好的一致性，而在额外颈部数量较多的情况下差异增大，这归因于有限元方法所显示的颈部有效长度的变化。根据空间的需求，所提出的方法可用于室内声学应用的可调谐吸声器。此外，这种方法可应用于声学乐器（如弦乐器）的额外可调谐空气共振的情况。
