Absorption of oblique incidence sound by a finite micro-perforated panel absorber

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While the structural-acoustic coupling between flexible structures and closed acoustic cavities has been extensively studied in the literature, the modeling of structures coupled through open cavities, especially connected in cascade, is still a challenging task for most of the existing methods. The possible presence of micro-perforated panels (MPPs) in such systems adds additional difficulties in terms of both modeling and physical understanding. In this study, a sub-structuring methodology based on the Patch Transfer Function (PTF) approach with a Compound Interface treatment technique, referred to as CI-PTF method, is proposed, for dealing with complex systems involving cascade open/closed acoustic cavities and MPPs. The co-existence of apertures and solid/flexible/micro-perforated panels over a mixed separation interface is characterized using a compound panel subsystem, which enhances the systematic coupling feature of the PTF framework. Using several typical configurations, the versatility and efficiency of the proposed method is illustrated. Numerical studies highlight the physical understanding on the behavior of MPP inside a complex vibroacoustic environment, thus providing guidance for the practical design of such systems.

Section: Introductionmentioning

confidence: 99%

Modeling vibroacoustic systems involving cascade open cavities and micro-perforated panels

Guyader

2014

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“…The dependence of the absorption performance of MPPs on various parameters has been discussed. 17 Apart from the normal incidence, studies on MPP absorbers under more complex working conditions, such as irregular-shaped backing cavity, 18 oblique incidence, 19 or in coupled vibroacoustic environment, 20 etc., have also been reported in the literature. Owing to the nonfibrous, incombustible, and cleanable feature, MPP absorbers have found their uses in a wide range of engineering applications.…”

Section: Introductionmentioning

confidence: 99%

Hybrid silencers with micro-perforated panels and internal partitions

You

2015

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A sub-structuring approach, along with a unit cell treatment, is proposed to model expansion chamber silencers with internal partitions and micro-perforated panels (MPPs) in the absence of internal flow. The side-branch of the silencer is treated as a combination of unit cells connected in series. It is shown that, by connecting multiple unit cells with varying parameters, the noise attenuation bandwidth can be enlarged. With MPPs, the hybrid noise attenuation mechanism of the silencer is revealed. Depending on the size of the perforation hole, noise attenuation can be dominated by dissipative, reactive, or combined effects together. For a broadband sound absorption, the hole size, together with the perforation ratio and other parameters, can be optimized to strike a balance between the dissipative and reactive effect, for ultimately achieving the desired noise attenuation performance within a prescribed frequency region. The modular nature of the proposed formulation allows doing this in a flexible, accurate, and cost effective manner. The accuracy of the proposed approach is validated through comparisons with finite element method and experiments.

“…MPP absorbers have been applied to various practical problems, for example, in communication rooms, 5 auditoriums, 6 windows, 7 duct silencers, [8][9][10][11] cylinders, 12 and noise barriers. 13 To improve the absorption performance, irregular shaped backings [14][15][16][17] or electromechanical approaches [18][19][20][21] have been suggested and the applicability of an MPP absorber is even now expanded. As for an MPP itself, effects of the hole shape have been investigated with the techniques of computational fluid dynamics 22,23 and the vibroacoustic behaviors have also been studied in detail and utilized to enhance the performance.…”

Section: Introductionmentioning

confidence: 99%

Numerical analyses of the sound absorption of cylindrical microperforated panel space absorbers with cores

Toyoda

Fujita

Sakagami

2015

Microperforated panels (MPPs) are next-generation absorption materials because they can provide wideband sound absorption without fibrous materials and can be composed of diverse materials to meet global environmental demands. The fundamental absorbing mechanism is Helmholtz-resonance absorption due to perforations and an air cavity. MPPs are typically backed by rigid flat walls, but to reduce the restrictions on the MPP absorber properties, one of the authors has proposed MPP space sound absorbers without backing structures, including three-dimensional cylindrical microperforated panel space absorbers (CMSAs). Advantages of MPPs without backing structures are design flexibility and ease of use. Besides, the absorption characteristics of a CMSA with a core, which has a rigid cylindrical core inside the CMSA, have been experimentally tested, but a method to predict the absorption characteristics is necessary to design CMSAs with cores. Herein the two-dimensional combined Helmholtz integral formulation method is employed, and its prediction accuracy is evaluated by comparing the measured and predicted absorption characteristics of a CMSA with a core. Furthermore, a parametric study with regard to the core size is carried out to investigate the transition of the absorbing mechanism.