On the Acousto-Elastic Behaviour of Double-Wall Panels With a Viscothermal Air Layer

Basten, T.G.H.; Hoogt, P.J.M. van der; Spiering, R.M.E.J.; Tijdeman, H.

doi:10.1006/jsvi.2000.3431

Cited by 25 publications

(35 citation statements)

References 12 publications

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“…The viscous shear forces, induced in the air layer near the enclosing surfaces, become more effective at relatively smaller gaps, and thus increase the damping. Basten et al 19,20 developed a modal model for double walls while taking into account the viscothermal effects in the air layer. It was shown that the damping of the so-called pumping modes of the plate can be largely increased by decreasing the thickness of the air layer.…”

Section: Introductionmentioning

confidence: 99%

Sound transmission through finite lightweight multilayered structures with thin air layers

Dijckmans

Vermeir

Lauriks

2010

The Journal of the Acoustical Society of America

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The sound transmission loss (STL) of finite lightweight multilayered structures with thin air layers is studied in this paper. Two types of models are used to describe the vibro-acoustic behavior of these structures. Standard transfer matrix method assumes infinite layers and represents the plane wave propagation in the layers. A wave based model describes the direct sound transmission through a rectangular structure placed between two reverberant rooms. Full vibro-acoustic coupling between rooms, plates, and air cavities is taken into account. Comparison with double glazing measurements shows that this effect of vibro-acoustic coupling is important in lightweight double walls. For infinite structures, structural damping has no significant influence on STL below the coincidence frequency. In this frequency region, the non-resonant transmission or so-called mass-law behavior dominates sound transmission. Modal simulations suggest a large influence of structural damping on STL. This is confirmed by experiments with double fiberboard partitions and sandwich structures. The results show that for thin air layers, the damping induced by friction and viscous effects at the air gap surfaces can largely influence and improve the sound transmission characteristics.

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Section: Introductionmentioning

confidence: 99%

Sound transmission through finite lightweight multilayered structures with thin air layers

Dijckmans

Vermeir

Lauriks

2010

The Journal of the Acoustical Society of America

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“…• Wave propagation in in-ear hearing aids [1] • The behavior of MEMS devices with thin fluid layers [2,3,4] • The behavior of microphones, consisting of a membrane backed by a thin air layer [5,6,7,8] • The behavior of inkjet print heads, including the wave propagation in narrow ink channels [9,10] • The behavior of plates and double wall panels with a thin fluid layer for reduction of sound transmission [11,12,13,14,15,16,17] • Modeling wave propagation in the cochlea [18] • Modeling wave propagation in the vocal tract, trachea and lungs [19] Note that in many cases where the boundary-layer thicknesses are small compared to the dimensions of the domain, neglecting viscothermal effects leads to a very accurate and efficient description of the fluid behavior. Nevertheless, a second class of problems where the viscothermal effects can become significant, even if the boundary-layer thicknesses are relatively small, is in systems near resonance.…”

Section: Applications Of Viscothermal Modelsmentioning

confidence: 99%

“…Deriving the dispersion equation requires the analytical solution of a vector Helmholtz equation, which is available for six orthogonal coordinate systems only (see section 3.2.3 or [73,74]). All geometries that can be modeled are bound by the coordinate surfaces 16 of these systems, limiting the use of this method to simple geometric shapes (while other considerations concerning the boundary conditions, limit the number of suitable geometries even further). The method yields a countable infinite number of modes, both propagating and evanescent in nature.…”

Section: (F)(g) Kirchhoff Modelsmentioning

confidence: 99%

“…In order to detect possible adverse or beneficial effects due to structured ordering of elements, all mesh patterns depicted in figure 5.2 are considered on regular meshes and distorted meshes 16 . Note that two types of distortions are considered.…”

Section: Boundary Conditionsmentioning

confidence: 99%

“…The first type of distortion is achieved by using a mapping that globally distorts the 16 In the presented results, the MINI and Crouzeix Raviart elements are only used in combination with the so-called Union Jack.…”

Section: Boundary Conditionsmentioning

confidence: 99%

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Viscothermal wave propagation

Nijhof¹

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SummaryIn engineering practice, the simplest, most efficient model that yields the desired level of accuracy is usually the model of choice. This is particulary true if an optimization process is involved, in which case the choice of the underlying models is often a trade-off between efficiency and accuracy. It is therefore important to know not only how efficient a model is, but also how accurate.In this work, the accuracy, efficiency and range of applicability of various (approximate) models for viscothermal wave propagation are investigated in a general setting. Models for viscothermal wave propagation describe the wave behavior of fluids including viscous and thermal effects. Cases where viscothermal effects are significant generally involve small fluid domains, low frequencies, or fluid systems near resonance. Examples of practical applications of these models are, for instance, describing the behavior of in-ear hearing aids, MEMS devices, microphones, inkjet printheads and muffler systems involving acoustic resonators.Amongst the various models for viscothermal wave propagation that are considered, a prominent role is taken by the family of approximate models known as Low Reduced Frequency (or LRF) models. These are the most efficient approximate models available and they have been used extensively to model a wide variety of problems involving viscothermal wave propagation. Nevertheless, LRF models are only available for a limited number of geometries and can become inaccurate under certain conditions. A second family of models that is considered consists of exact solutions to the equations describing viscothermal wave propagation. These models, which are less efficient than the LRF models, provide reference solutions which can be used to determine the accuracy of the LRF models. A drawback of the exact models is that they are only available for a small number of geometries. Therefore a third family of models is considered, which is based on a newly developed Finite Element (or FE) approximation of the equations for viscothermal wave propagation. The main attraction of these FE models is that they can be used to model arbitrary geometries and boundary conditions. A drawback is that obtaining a solution requires much more computing power than needed for the LRF or exact models. The vi numerical stability and convergence properties of the developed FE methods are investigated to ensure that they can yield reference solutions of a desired accuracy for cases where an exact solution is not available.Using these three families of models, a number of parameter studies are carried out that yield detailed information on accuracy of the highly efficient LRF models for a range of geometries and boundary conditions. The gathered data provides a means of estimating the accuracy of simple coupled LRF models a priori.Besides the investigation into the accuracy of LRF models, two engineering applications where viscothermal wave propagation takes a prominent role are described. The first application involves the passive si...

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Aeroacoustic Research in Europe: The Ceas-Asc Report on 2000 Highlights

Ianniello

2002

Journal of Sound and Vibration

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On the Acousto-Elastic Behaviour of Double-Wall Panels With a Viscothermal Air Layer

Cited by 25 publications

References 12 publications

Sound transmission through finite lightweight multilayered structures with thin air layers

Sound transmission through finite lightweight multilayered structures with thin air layers

Viscothermal wave propagation

Aeroacoustic Research in Europe: The Ceas-Asc Report on 2000 Highlights

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