Interior noise reduction of composite cylinders using distributed vibration absorbers

Osman, Haisam; Johnson, Marty; Fuller, Chris R.; Marcotte, Pierre

doi:10.2514/6.2001-2230

Cited by 10 publications

(7 citation statements)

References 6 publications

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“…These include source reduction methods, active [4,5] and passive [6,7] control of the aircraft transmission paths as well as the active control of the sound field [8,9]. Another approach is to install (partially damped) resonant devices such as Helmholtz resonators and distributive vibration absorbers [10][11][12] to reduce the fuselage vibrations or to damp the cabin's acoustic resonances.…”

Section: Introductionmentioning

confidence: 99%

“…They have been proven to offer broad-band control of noise transmission into cylinders [10,12] due to the fact that they combine two effects: acoustic absorption by the acoustic foam (elastic layer) at high frequencies and the reduction of efficiently sound radiating structural modes at low frequencies. HG blankets represent an extension of this idea by distributing the dynamic vibration absorbers over the whole structure by inserting a number of masses into the elastic material which blankets the entire structure (or large portions of the structure).…”

Section: Introductionmentioning

confidence: 99%

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An Analytical Model for the Interaction of Mass Inclusions in Heterogeneous (HG) Blankets

Wagner

Johnson

Idrisi

et al. 2011

Journal of Vibration and Acoustics

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The heterogeneous (HG) blanket is a passive treatment used to reduce the low frequency transmission of sound through partitions. HG blankets, glued onto a structure, consist of an elastic medium with embedded mass inhomogeneities that mechanically replicate a mass-spring-damper system to reduce efficient radiating structural modes at low frequencies. The elastic layer typically used has sound absorption properties to create a noise control device with a wide bandwidth of performance. The natural frequency of an embedded dynamic vibration absorber is determined by the mass of the inhomogeneity as well as by its effective stiffness due to the interaction of the mass inclusion with the elastic layer. A novel analytical approach has been developed to describe in detail the interaction of the mass inclusions with the elastic layer and the interaction between the masses by evaluating special elastomechanical concepts. The effective stiffness is predicted by the analytical approach based on the shape of the mass inclusions as well as on the thickness and material properties of the layer. The experimental validation is included and a simplified direct equation to calculate the effective stiffness of a HG blanket is proposed. Furthermore, the stress field inside the elastic material will be evaluated with focus on the stresses at the base to assess the modeling of one or more masses placed on top of the elastic layer as dynamic vibration absorbers. Finally, the interaction between two (or more) masses placed onto the same layer is studied with special focus on the coupling of the masses at low distances between them.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

An Analytical Model for the Interaction of Mass Inclusions in Heterogeneous (HG) Blankets

Wagner

Johnson

Idrisi

et al. 2011

Journal of Vibration and Acoustics

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“…Using a variety of mass area densities and by altering the effective spring transverse stiffness by changing the woven layer characteristics, DVAs can be tuned over a large range of frequencies. The DVA was recently studied by Marcotte 2 in depth and has been applied to a variety of structures, for instance large cylindrical shells 3,4 .…”

Section: Introductionmentioning

confidence: 99%

Passive distributed vibration absorbers for low frequency noise control

Fuller

Harne²

2010

ncej

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It is well known that standard poroelastic materials and viscoelastic damping materials are ineffective at reducing low frequency sound and vibration. This paper overviews two new treatments developed at Virginia Tech which attempt to address this problem. Heterogeneous blankets consist of poroelastic material with embedded multiple small masses. The masses combine with the natural elasticity of the poroelastic material matrix to create multiple embedded vibration absorbers with a range of natural frequencies in the low frequency region. The embedded masses are found to significantly increase the low frequency transmission loss and absorption of the poroelastic material. The second treatment, distributed vibration absorbers, spread mass and spring elements over a large area while still maintaining a viable reactive damping effect at low frequencies. DVAs are found to provide global reduction of low frequency vibration of structures in a compact, lightweight configuration. The paper will summarize the concepts, development and testing of both devices. Applications of the new treatments to realistic structures will be considered.

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“…Due to the difficulties of predicting acoustic resonance using analytical or numerical methods, much of the work has been conducted experimentally, similar to the shaker excitations used for modal extraction in structural engineering. A classical approach to establish possible links between observed instabilities and acoustic resonances is based on white-noise excitation of the component under study and the filtering of acoustic resonance frequencies by using loudspeakers [10][11][12][13][14]. In many cases, such experimental simple acoustic characterization may well provide crucial information about flow-induced resonant sound generation during operating conditions [15,16].…”

Section: Introductionmentioning

confidence: 99%

A combined time and frequency domain approach for acoustic resonance prediction

Chassaing

Sayma

Imregun

2008

Journal of Sound and Vibration

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This is the accepted version of the paper.This version of the publication may differ from the final published version.Permanent repository link: http://openaccess.city.ac.uk/7905/ Link to published version: http://dx. AbstractA general time and frequency methodology has been developed to identify acoustic resonance conditions of internal flow configurations. The resonant frequencies and the corresponding acoustic modes are determined by imposing onto the flow a time-dependent excitation at several locations on the boundary. The resulting time-domain responses of the pressure signals, which are computed via an unsteady Favre-Reynolds averaged Navier-Stokes solver, are used to determine the frequency response function matrix of the fluid which can be considered to be a multipleinput multiple-output system. The main test case was selected to be a closed-end cylindrical duct for which the effect of different excitation techniques on the predicted resonant acoustic field is discussed in detail. The last test case deals with the acoustic characterization of a 2-D channel with symmetric bumps and an inlet flow velocity of 17 ms −1 . It is shown that the methodology was suitable for identifying both axial and transverse acoustic modes in a 10 Hz -3 kHz frequency range.

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Interior noise reduction of composite cylinders using distributed vibration absorbers

Cited by 10 publications

References 6 publications

An Analytical Model for the Interaction of Mass Inclusions in Heterogeneous (HG) Blankets

An Analytical Model for the Interaction of Mass Inclusions in Heterogeneous (HG) Blankets

Passive distributed vibration absorbers for low frequency noise control

A combined time and frequency domain approach for acoustic resonance prediction

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