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  • 1.
    Alberdi-Muniain, Ane
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, MWL Strukturakustik.
    Gil-Negrete, N
    Kari, Leif
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, MWL Strukturakustik.
    Indirect energy flow measurement in magneto-sensitive vibration isolator systems2013Ingår i: Applied Acoustics, ISSN 0003-682x, ISSN 0003-682x, Vol. 74, nr 4, s. 575-584Artikel i tidskrift (Övrigt vetenskapligt)
    Abstract [en]

    The indirect energy flow measurement method is extended to cover highly nonlinear, frequency, amplitude and magnetic field dependent magneto-sensitive natural rubber isolators applied in a real vibration isolation system. Energy flow is an effective measure of vibration isolation while being a single quantity that considers both force and velocity. The use of the indirect technique is of interest while requiring only accelerometers since it is usually difficult to directly measure the force in a real application. The vibration isolation system is composed of four magneto-sensitive rubber isolators that are inserted under a vibrating source consisting of a solid aluminium mass excited by an electro-dynamic shaker. Magneto-sensitive rubber isolators are more useful than conventional rubber isolators since the dynamic stiffness varies with the application of an external magnetic field, thus resulting in more effective vibration isolation. Various approximations regarding the indirect technique are investigated, concluding that average stiffness of magneto-sensitive isolators can be used and auto-spectrum of the foundation velocity ignored. In addition, various error analyses are performed. Finally, the indirect measurement of the energy flow is validated by direct measurements, showing very good agreement.

  • 2.
    Cameron, Christopher John
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg.
    Wennhage, Per
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg.
    Göransson, Peter
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg.
    Prediction of NVH behaviour of trimmed body components in the frequency range 100-500 Hz2010Ingår i: Applied Acoustics, ISSN 0003-682x, Vol. 71, nr 8, s. 708-721Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The work within this paper focuses on the application and validation of numerical methods for predicting the acoustic and structural NVH behaviour of trimmed body components in an automotive context. In particular, the level of modelling refinement and accuracy necessary to establish a reliable finite element analysis model for comparative purposes in the development of alternative designs is investigated. Specifically, the roof structure of a passenger car was investigated from various performance aspects, using both structural and acoustic excitation. The roof was initially tested in situ, with and without interior lining, to provide a reference for subsequent component tests. It was then detached from the car, mounted in a stiff frame and tested in a transmission window using both acoustic and structural excitation. A finite element model of the detached component was developed using shell and solid elements for the structure and solid elements for the interior lining. Predictions were carried out to evaluate the STL as well as the vibrational frequency response due to a force applied to the structure. Special attention was given to the modelling of the headliner as well as the air gap separating the headliner from the outer sheet metal. A sensitivity study of various headliner properties was performed in addition to a comparison between solutions calculated using standard Nastran elements and augmented poro-elastic elements via the software package CDH/EXEL. The main objective of the current work has been to establish a datum reference for alternative designs. From this aspect, the validation of the numerical modelling methodology, in particular the level of detail and accuracy used, was a crucial step. It was found that the predictions agreed very well with the measured data. As an additional, very interesting result, it was also found that the in situ testing correlated well with the transmission suite testing.

  • 3.
    Dickson, Crispin
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, MWL Marcus Wallenberg Laboratoriet.
    Bolin, Karl
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, MWL Marcus Wallenberg Laboratoriet.
    Continuous judgment by category-ratio scaling of aircraft noise2014Ingår i: Applied Acoustics, ISSN 0003-682x, Vol. 84, s. 3-8Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A continuous judgment by category-ratio (CJCR) scaling method was used to evaluate the instantaneous annoyance of original and modified aircraft sounds. The result from the proposed method resulted in a temporal stream of annoyance levels for the whole flyover sequence that could be further analyzed. The test subjects were continuously rating their instantaneous annoyance on a Borg CR 100 scale (R) during the playback of 10 flyover sequences. Using a category-ratio (CR) scale instead of a category (C) scale, mathematical operations such as calculations of average were enabled but gave also advantages in terms of higher resolution in the responses. The results showed differences in perception in the time segment where the sound had been modified. The temporal stream of annoyance was also converted into overall judgments of the sounds, these estimations showed consistency with previous results obtained using the semantic differential and paired comparison method.

  • 4.
    Färm, Anna
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, MWL Marcus Wallenberg Laboratoriet. Scania CV AB, Sweden.
    Boij, Susann
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, MWL Marcus Wallenberg Laboratoriet.
    Glav, Ragnar
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, MWL Marcus Wallenberg Laboratoriet. Scania CV AB, Sweden.
    Dazel, Olivier
    Absorption of sound at a surface exposed to flow and temperature gradients2016Ingår i: Applied Acoustics, ISSN 0003-682x, Vol. 110, s. 33-42Artikel i tidskrift (Övrigt vetenskapligt)
    Abstract [en]

    In noise abatement using porous or fibrous materials, accurate determination of the surface impedance representing the absorber is decisive for simulation quality. The presence of grazing flow and non-homogeneous ambient temperature influence the reaction of the absorber and may suitably be included in a modified “effective” surface impedance. In this paper, this approach is applied to a generic case representative for the engine bay of a heavy truck, where porous shields suppress the radiated noise, e.g. during a pass-by noise test. The change in the absorption is determined numerically by solving the wave propagation through a layer of varying temperature and flow adjacent to the impedance surface for different angles of incidence. The study shows significant impact of both flow and temperature, especially for materials with low absorption. The diffuse field absorption coefficient is also derived and although the effect is less pronounced in this case, it is still important in lower frequencies and in the frequency range typical for IC engine noise. The proposed numerical method is shown to be accurate and efficient for determination of the effective impedance and moreover not limited to thin boundary layers.

  • 5.
    Lindberg, Eskil
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, MWL Strukturakustik.
    Östberg, Martin
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, MWL Strukturakustik.
    Hörlin, Nils-Erik
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, MWL Strukturakustik.
    Göransson, Peter
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, MWL Strukturakustik.
    A vibro-acoustic reduced order model using undeformed coupling interface substructuring - Application to rubber bushing isolation in vehicle suspension systems2014Ingår i: Applied Acoustics, ISSN 0003-682x, Vol. 78, s. 43-50Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A vibro-acoustic reduced order model (ROM) based on a substructuring method using undeformed coupling interfaces (UCI) is proposed. The method may be used to reduce the order of a global problem, this by subdividing the global system to substructures interacting through UCI's. The local dynamic stiffness of each substructure may then be modelled with a, for that particular problem, best suited description. The feasibility of the method is demonstrated by a sensitivity analysis of the vibro-acoustic power isolation in a vehicle suspension system, comprising of a link arm connected to a vehicle car body through two rubber bushings. The link arm ROM is a component mode synthesis (CMS)-UCI, the rubber bushing model is a UCI-ROM derived from a 2D axisymmetric model using a frequency dependent visco-elastic material model. Finally the car body model is a frequency dependent UCI-ROM from a full car body finite element model. It is shown that the UCI-ROM approach efficiently can be used for parametric studies on a substructure level. The results suggest that the performed reorientation of the rubber bushings can alter, with orders of magnitude, the energy flow into the car.

  • 6.
    O'Reilly, Ciarán J.
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg. KTH, Skolan för teknikvetenskap (SCI), Centra, VinnExcellence Center for ECO2 Vehicle design.
    A wave expansion method for acoustic propagation in lined flow ducts2015Ingår i: Applied Acoustics, ISSN 0003-682x, Vol. 90, s. 54-63Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Acoustic liners are used extensively in engineering applications, particularly in aero-engines and automotive exhaust systems. In this paper, a flow impedance boundary conditions is introduced into the wave expansion method with the aim of providing an efficient methodology for computing the acoustic propagation through a lined duct with flow. For a potential flow, the boundary layer and the lined wall are included in the discretisation scheme by the Myers flow impedance boundary condition. The acoustic propagation through a flow impedance tube is computed in order to validate the implementation of the impedance boundary condition in this scheme. The results show that this computationally light methodology provides generally good agreement with the experimental data.

  • 7.
    Pignier, Nicolas J.
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg. KTH, Skolan för teknikvetenskap (SCI), Centra, VinnExcellence Center for ECO2 Vehicle design.
    O'Reilly, Ciarán J.
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg. KTH, Skolan för teknikvetenskap (SCI), Centra, VinnExcellence Center for ECO2 Vehicle design.
    Boij, Susann
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg. KTH, Skolan för teknikvetenskap (SCI), Centra, VinnExcellence Center for ECO2 Vehicle design.
    A Kirchhoff approximation-based numerical method to compute multiple acoustic scattering of a moving source2015Ingår i: Applied Acoustics, ISSN 0003-682x, Vol. 96, s. 108-117Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Within the scope of a study of external noise propagation from moving ground vehicles, a numerical method is developed to compute the acoustic field emitted by a moving source in the presence of scattering objects such as roads, buildings or noise-shields. This method is developed with the purpose of being used in a vehicle design process and therefore it must have a low computational cost, which requires a certain number of approximations. The case of a fixed point source is studied first then the effect of a movement of the source is taken into account through the introduction of a retarded time. The acoustic source is assumed to be represented by one or many harmonic monopoles of possibly different frequency moving with a constant speed in a quiescent flow field. Scattering from nearby perfectly reflecting objects is computed through a Kirchhoff–Helmholtz integral equation applying the Kirchhoff approximation. A ray-surface intersection algorithm to compute shadow areas is proposed. The method is validated against analytical solutions and experimental results for a fixed source, and against a higher-order finite difference time-domain method for the multiple scattering of a moving source. Results are good and show that this method can potentially be used to predict urban noise.

  • 8.
    Thompson, David
    et al.
    Institute of Sound and Vibration Research, University of Southampton.
    Squicciarini, Giacomo
    Institute of Sound and Vibration Research, University of Southampton.
    Zhang, Jin
    Institute of Sound and Vibration Research, University of Southampton.
    Lopez Arteaga, Ines
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, MWL Marcus Wallenberg Laboratoriet.
    Zea, Elias
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, MWL Marcus Wallenberg Laboratoriet.
    Dittrich, Michael
    TNO, Den Haag, The Netherlands.
    Jansen, Erwin
    TNO, Den Haag, The Netherlands.
    Arcas, Kevin
    Ingeniería para el Control del Ruido, Barcelona, Spain.
    Cierco, Ester
    Ingeniería para el Control del Ruido, Barcelona, Spain.
    Magrans, Francesc Xavier
    Ingeniería para el Control del Ruido, Barcelona, Spain.
    Malkoun, Antoine
    Alstom Transport, Reichshoffen, France.
    Iturritxa, Egoitz
    CAF, Beasain, Spain.
    Guiral, Ainara
    CAF, Beasain, Spain.
    Stangl, Matthias
    DB Systemtechnik, München, Germany.
    Schleinzer, Gerald
    Siemens, Graz, Austria.
    Martin Lopez, Beatriz
    Patentes Talgo S.L., Madrid, Spain.
    Chaufour, Claire
    SNCF Innovation & Recherche, Paris, France.
    Wändell, Johan
    Bombardier Transportation Acoustic Department, Hennigsdorf, Germany.
    Assessment of measurement-based methods for separating wheel and track contributions to railway rolling noise2018Ingår i: Applied Acoustics, ISSN 0003-682x, Vol. 140, s. 48-62Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The noise produced during a train pass-by originates from several different sources such as propulsion noise, noise from auxiliary equipment, aerodynamic noise and rolling noise. The rolling noise is radiated by the wheels and the track and is excited by the wheel and rail unevenness, usually referred to as roughness. The current TSI Noise certification method, which must be satisfied by all new mainline trains in Europe, relies on the use of a reference track to quantify the noise from new vehicles. The reference track is defined by an upper limit of the rail roughness and a lower limit of the track decay rate (TDR). However, since neither the rail roughness nor the track radiation can be completely neglected, the result cannot be taken as representing only the vehicle noise and the measurement does not allow separate identification of the noise radiated by wheel and track. It is even likely that further reductions in the limit values for new rolling stock cannot be achieved on current tracks. There is therefore a need for a method to separate the noise into these two components reliably and cheaply. The purpose of the current study is to assess existing and new methods for rolling noise separation. Field tests have been carried out under controlled conditions, allowing the different methods to be compared. The TWINS model is used with measured vibration data to give reference estimates of the wheel and track noise components. Six different methods are then considered that can be used to estimate the track component. It is found that most of these methods can obtain the track component of noise with acceptable accuracy. However, apart from the TWINS model, the wheel noise component could only be estimated directly using three methods and un- fortunately these did not give satisfactory results in the current tests.

  • 9.
    Zea, Elias
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, MWL Marcus Wallenberg Laboratoriet.
    Lopez Arteaga, Ines
    KTH, Skolan för teknikvetenskap (SCI), Farkost och flyg, MWL Marcus Wallenberg Laboratoriet. Eindhoven University of Technology, Department of Mechanical Engineering.
    Sound field separation for planar sources facing a parallel reflector2019Ingår i: Applied Acoustics, ISSN 0003-682x, Vol. 149C, s. 181-191Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We consider the problem of separating and reconstructing the sound field radiated by a planar source, e.g. a vibrating plate, that faces a parallel reflector. For this purpose we propose a Fourier-based technique to process near-field microphone array measurements that are performed on a single plane between the plate and the reflector. A closed-form expression is derived in the wavenumber domain to recover the free-space sound field radiated by the plate. The fundamental assumption is that the plate scatters sound in a locally-reacting fashion. Overall, provided the admittances of the plate and the reflecting surface are known, the results demonstrate that it is possible to recover the free-field sound radiated by the plate with a reasonable accuracy.

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