Abstract Helmholtz resonators are commonly used as narrowband sound absorbers in room acoustics applications. Previous research has shown that Helmholtz resonators can also be used to improve the sound transmission loss of double walls. The focus of this paper is the broadband improvement of the transmission loss of double walls in the low frequency region by tuning the Helmholtz resonators inside the cavity to frequencies lower or higher than the mass-air-mass resonance frequency of the double wall. A new analytical model using the effective material parameters (bulk modulus and density) of a fluid volume containing Helmholtz resonators is developed to describe the vibro-acoustic behavior of double walls with Helmholtz resonators. Using this model it can be shown that by tuning the Helmholtz resonators properly, the mass-air-mass resonance frequency of the unmodified double wall can be shifted significantly, leading to an improvement of the transmission loss of the double wall roughly between the mass-air-mass resonance frequency and the resonance frequency of the resonators. This improvement, however, comes along with a decrease of the transmission loss at high frequencies due to a decoupling of the Helmholtz resonators which is also covered by the proposed analytical model. Parametric studies are performed to identify relevant design parameters to optimize the transmission loss improvement by the Helmholtz resonators. Finally, experimental results of different double wall designs with integrated Helmholtz resonators are presented to validate the proposed analytical model and demonstrate the effectiveness under diffuse field incidence.

中文翻译：

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亥姆霍兹共振器双壁宽带低频传声损耗改善

摘要 Helmholtz 谐振器通常用作室内声学应用中的窄带吸声器。之前的研究表明，亥姆霍兹共振器也可以用来改善双壁的声音传输损失。本文的重点是通过将腔内的亥姆霍兹谐振器调谐到低于或高于双壁质量-空气-质量共振频率的频率，在低频区域改善双壁的传输损耗。使用包含亥姆霍兹谐振器的流体体积的有效材料参数（体积模量和密度）开发了一种新的分析模型，以描述具有亥姆霍兹谐振器的双壁的振动声学行为。使用这个模型可以证明，通过适当调整亥姆霍兹谐振器，未修改的双壁的质量-空气-质量共振频率可以显着偏移，导致双壁的传输损耗改善大致在质量-空气-质量共振频率和共振器的共振频率之间。然而，这种改进伴随着高频传输损耗的降低，这是由于亥姆霍兹谐振器的去耦，这也包含在所提出的分析模型中。执行参数研究以确定相关设计参数，以优化亥姆霍兹谐振器的传输损耗改进。最后，展示了具有集成亥姆霍兹谐振器的不同双壁设计的实验结果，以验证所提出的分析模型并证明在漫射场入射下的有效性。