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  • 1.
    Feng, Leping
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, MWL Structural and vibroacoustics.
    Ramanathan, Sathish Kumar
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, MWL Structural and vibroacoustics.
    On application of radiation loss factor in the prediction of sound transmission loss of a honeycomb panel2012In: International Journal of Acoustics and Vibration, ISSN 1027-5851, Vol. 17, no 1, p. 47-51Article in journal (Refereed)
    Abstract [en]

    The application of the radiation loss factor in the prediction of sound transmission loss of a lightweight, orthotropic sandwich panel is investigated in this paper. Comparisons with measurements show that predictions often underestimate the sound transmission loss of the panel around the corresponding critical frequency when the measured loss factor, which in principle includes the radiation loss factor, is used. This is due to the measurement methods used for the loss factor and the band average. It is thus recommended to use the loss factor measured at low frequencies plus the theoretical radiation loss factor in order to improve the prediction of the sound transmission loss of a honeycomb panel around the critical frequency.

  • 2.
    Feng, Leping
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, MWL Structural and vibroacoustics.
    Ramanathan, Sathish Kumar
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, MWL Structural and vibroacoustics.
    On application of radiation loss factor in the prediction of sound transmission loss of a honeycomb panel2010In: 17th International Congress on Sound and Vibration 2010, ICSV 2010: Volume 3, 2010, p. 1862-1869Conference paper (Refereed)
    Abstract [en]

    The application of the radiation loss factor in the prediction of sound transmission loss of a lightweight, orthotropic sandwich panel is investigated in this paper. Comparisons between measurements and predicted results show that predictions often underestimate the sound transmission loss of the panel around the corresponding critical frequency when a measured loss factor, which in principle includes the radiation loss factor, is used. This is due to the methods used for the loss factor measurements and due to the fact that the band average loss factor is applied in the calculation. It is recommended to use the material loss factor measured at low frequencies plus the narrow band, theoretical radiation loss factor in order to improve the prediction of the sound transmission loss of a honeycomb panel around the critical frequency.

  • 3. Orrenius, U.
    et al.
    Wareing, A.
    Ramanathan, Sathish Kumar
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, MWL Structural and vibroacoustics.
    Prediction and control of sound transmission through honeycomb sandwich panels for aircraft fuselage and train floors2010In: 17th International Congress on Sound and Vibration 2010, ICSV 2010: Volume 1, 2010, p. 117-124Conference paper (Refereed)
    Abstract [en]

    Composite sandwich structures with honeycomb cores are increasingly considered as an alternative to aluminium for aircraft fuselages. Technical benefits include lower density, higher strength and greater fatigue resistance. The ability of composite materials to inexpensively be formed into complex shapes allows part count reductions and substantial cost savings. For railway carbodies, metal honeycomb sandwich panels are common in door panels and for interior floors. For floors the drivers are low weight, good moisture properties, fire resistance combined with high stiffness. Despite these advantages, sandwich structures may exhibit increased sound transmission compared to homogenous structures. Appropriate choice of core materials will reduce the need for subsequent noise control measures. In this paper it is shown how a physical understanding for the wave transmission phenomena together with modern prediction software, can be used to achieve designs that satisfy both acoustical and structural requirements. Calculated wavenumbers and transmission losses are compared to measurements for composite sandwich panels with honeycomb cores, treated and un-treated with damping layers. Modeling concepts as well as the potential for insertion losses due to added damping are discussed.

  • 4.
    Ramanathan, Sathish Kumar
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Marcus Wallenberg Laboratory MWL.
    Sound transmission properties of honeycomb panels and double-walled structures2012Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Sandwich panels with aluminium face sheets and honeycomb core material have certain advantages over panels made of wood. Some of the advantages of these constructions are low weight, good moisture properties, fire resistance and high stiffness to-weight ratio etc. As product development is carried out in a fast pace today, there is a strong need for validated prediction tools to assist during early design stages. In this thesis, tools are developed for predicting the sound transmission through honeycomb panels, typical for inner floors in trains and later through double-walled structures typical for rail-vehicles, aircrafts and ships.

    The sandwich theory for wave propagation and standard orthotropic plate theory is used to predict the sound transmission loss of honeycomb panels. Honeycomb is an anisotropic material which when used as a core in a sandwich panel, results in a panel with anisotropic properties. In this thesis, honeycomb panels are treated as being orthotropic and the wavenumbers are calculated for the two principal directions. The wavenumbers are then used to calculate the sound transmission using standard orthotropic theory. These predictions are validated with results from sound transmission measurements. The influence of constrained layer damping treatments on the sound transmission loss of these panels is investigated. Results show that, after the damping treatment, the sound transmission loss of an acoustically bad panel and a normal pane lare very similar.

    Further, sound transmission through a double-leaf partition based on a honeycomb panel with periodic stiffeners is investigated. The structural response of the periodic structure due to a harmonic excitation is expressed in terms of a series of space harmonics and virtual work theory is applied to calculate the sound transmission. The original model is refined to include sound absorption in the cavity and to account for the orthotropic property of the honeycomb panels. Since the solution of the space harmonic analysis is obtained in a series form, a sufficient number of terms has to be included in the calculation to ensure small errors. Computational accuracy needs to be balanced with computational cost as calculation times increases with the number of terms. A new criterion is introduced which reduces the computational time by up to a factor ten for the panels studied. For all the double-leaf systems analysed, the sound transmission loss predictions from the periodic model with the space harmonic expansion method are shown to compare well with laboratory measurements.

  • 5.
    Ramanathan, Sathish Kumar
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, MWL Structural and vibroacoustics.
    The effects of damping treatment on the sound transmission loss of honeycomb panels2010Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    In the industry, all passenger vehicles are treated with damping materials to reduce structure-borne sound. Though these damping materials are effective to attenuate structure-borne sound, they have little or no effect on the air-borne sound transmission.The lack of effective predictive methods for assessing the acoustic effects due to added damping on complex industrial structures leads to excessive use of damping materials.Examples are found in the railway industry where sometimes the damping material applied per carriage is more than one ton. The objective of this thesis is to provide a better understanding of the application of these damping materials in particular when applied to lightweight sandwich panels.

    As product development is carried out in a fast pace today, there is a strong need for validated prediction tools to assist in the design process. Sound transmission loss of sandwich plates with isotropic core materials can be accurately predicted by calculating the wave propagation in the structure. A modified wave propagation approach is used to predict the sound transmission loss of sandwich panels with honeycomb cores. The honeycomb panels are treated as being orthotropic and the wave numbers are calculated for the two principle directions. The orthotropic panel theory is used to predict the sound transmission loss of panels. Visco-elastic damping with a constraining layer is applied to these structures and the effect of these damping treatment on the sound transmission loss is studied. Measurements are performed to validate these predictions.

    Sound radiated from vibrating structures is of great practical importance.The radiation loss factor represents damping associated with the radiation of sound as a result of the vibrating structure and can be a significant contribution for structures around the critical frequency and for composite structures that are very lightly damped. The influence of the radiation loss factor on the sound reduction index of such structures is also studied.

  • 6.
    Ramanathan, Sathish Kumar
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, MWL Structural and vibroacoustics.
    Feng, Leping
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, MWL Structural and vibroacoustics.
    Orrenius, Ulf
    Effects of damping treatments on acoustic properties of honeycomb panels2008Conference paper (Refereed)
    Abstract [en]

    Damping treatment is a common way to reducestructural vibration and as well as sound radiation. Inthis paper the effects of applying constrainedvisco-elastic damping treatment on lightweighthoneycomb structures are studied. Honeycomb panelsare well known for their high strength to weight ratiobut they rather possess poor acoustic transmissionproperties necessitating the use of additional dampinglayer treatments. However, although added damping isusually effective for vibration reduction it has oftenlittle effect on sound transmission. This paper comparesthe acoustic properties of honeycomb panels withdifferent core thicknesses and honey comb structuresthrough laboratory measurements. Constrainedvisco-elastic damping layers are tried on these panelsand a solution for a possible optimized dampingtreatment is studied.

  • 7.
    Ramanathan, Sathish Kumar
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, MWL Structural and vibroacoustics.
    Feng, Leping
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, MWL Structural and vibroacoustics.
    Orrenius, Ulf
    Modelling the sound transmission through rib-stiffened sandwich double-leaf partitions using space harmonic analysisIn: Journal of Sound and Vibration, ISSN 0022-460X, E-ISSN 1095-8568Article in journal (Other academic)
  • 8.
    Ramanathan, Sathish Kumar
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, MWL Structural and vibroacoustics.
    Feng, Leping
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, MWL Structural and vibroacoustics.
    Orrenius, Ulf
    Modelling the sound transmissionthrough rib-stiffened double-leaf partitions with cavity absorptionIn: Journal of Sound and Vibration, ISSN 0022-460X, E-ISSN 1095-8568Article in journal (Other academic)
  • 9.
    Ramanathan, Sathish Kumar
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, MWL Structural and vibroacoustics.
    Feng, Leping
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, MWL Structural and vibroacoustics.
    Orrenius, Ulf
    Predicting the sound transmission loss of honeycomb panels using the wave propagation approach2011In: Acta Acoustica united with Acustica, ISSN 1610-1928, E-ISSN 1861-9959, Vol. 97, no 5, p. 869-876Article in journal (Refereed)
    Abstract [en]

    The sound transmission properties of sandwich panels can be predicted with sufficient degree of accuracy by calculating the wave propagation properties of the structure. This method works well for sandwich panels with isotropic cores but applications to panels with anisotropic cores are hard to find. Honeycomb is an example of anisotropic material which when used as a core, results in a sandwich panel with anisotropic properties. In this paper, honeycomb panels are treated as being orthotropic and the wavenumbers are calculated for the two principle directions. These calculated wavenumbers are validated with the measured wavenumbers estimated from the resonance frequencies of freely hanging honeycomb beams. A combination of wave propagation and standard orthotropic plate theory is used to predict the sound transmission loss of honeycomb panels. These predictions are validated through sound transmission measurements. Passive damping treatment is a common way to reduce structural vibration and sound radiation, but they often have little effect on sound transmission. Visco-elastic damping with a constraining layer is applied to two honeycomb panels with standard and enhanced fluid coupling properties. This enhanced fluid coupling in one of the test panels is due to an extended coincidence range observed from the dispersion curves. The influence of damping treatments on the sound transmission loss of these panels is investigated. Results show that, after the damping treatment, the sound transmission loss of an acoustically bad panel and a normal panel are very similar.

  • 10.
    Ramanathan, Sathish Kumar
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, MWL Structural and vibroacoustics.
    Feng, Leping
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, MWL Structural and vibroacoustics.
    Orrenius, Ulf
    Transmission loss of rib-stiffened double-leaf partitions with cavity absorption2012Conference paper (Refereed)
1 - 10 of 10
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  • ieee
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