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  • 1.
    Berglund, Per-Olof
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, MWL Structural and vibroacoustics.
    Åbom, Mats
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, MWL Flow acoustics.
    Feng, Leping
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, MWL Structural and vibroacoustics.
    An application of the noise synthesis technology (NST) to a system with an axial fan2002In: Forum Acustica 2002, Seville, Spain, 2002Conference paper (Refereed)
  • 2. Facian, Amparo
    et al.
    Nilsson, Anders
    KTH, Superseded Departments, Vehicle Engineering.
    Feng, Leping
    KTH, Superseded Departments, Vehicle Engineering.
    Nilsson, Eva
    KTH, Superseded Departments, Vehicle Engineering.
    Propagation of structure-borne sound in silencers used in power plants2004In: The 11th International Congress on Sound and Vibration, 2004, p. 1069-1076Conference paper (Refereed)
  • 3.
    Feng, Leiping
    KTH, Superseded Departments, Vehicle Engineering.
    An experimental method for vibrational insertion loss of mechanical joints2001In: Acustica, ISSN 0001-7884, Vol. 87, no 2, p. 191-198Article in journal (Refereed)
    Abstract [en]

    An experimental method is presented in this paper to determine vibro-acoustic properties of mechanical joints. A new quantity, vibrational insertion loss, which is the vibration reduction introduced by a joint and is used to describe vibro-acoustic performance of a mechanical joint in a finite system, is introduced. Two test-rigs are manufactured and tested for planar and non-planar joints. Results show that for well-defined joints, repeatability and reproducibility of the suggested parameter less than 2 dB can be achieved. Comparisons are also made between the vibrational insertion loss and the vibration level difference. It is illustrated that the vibration level difference can only detect the change of modal behaviour of the system, while the vibrational insertion loss can be used to detect both changes of modal behaviour and of system damping introduced by the insertion of the joint.

  • 4.
    Feng, Leiping
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, MWL Structural and vibroacoustics.
    Modified honeycomb panels to improve sound insulation properties2005In: Acta Acoustica united with Acustica, ISSN 1610-1928, E-ISSN 1861-9959, Vol. 91, no 2, p. 386-388Article in journal (Refereed)
    Abstract [en]

    A modified honeycomb panel with improved bonding technique is presented in this paper. The idea is to keep the basic mechanical properties of a honeycomb panel while to eliminate the coincidence phenomenon of the whole system by using modified bonding technique. A specimen was made and measurement was performed. Results show that the coincidence phenomenon of the whole system disappears and the weighted intensity sound reduction index is 4 dB higher than that of the corresponding honeycomb panel with similar surface density and static strength.

  • 5.
    Feng, Leiping
    KTH, Superseded Departments, Vehicle Engineering.
    Vibrational insertion loss of traditional and smart joints2001In: Acustica, ISSN 0001-7884, Vol. 87, no 2, p. 199-205Article in journal (Refereed)
    Abstract [en]

    The vibrational insertion loss of selected traditional and smart joints are investigated experimentally with the test-rigs presented in reference [1, 2]. The influences of various factors such as spacing between fasteners, overlap, bonding materials are examined. The relation between system damping and the damping introduced by the joint is discussed. For smart joints, comparison is also made with the transmission loss of elastic interlayer in order to understand the mechanism. At low frequencies the main positive effect of a joint is damping. When the frequency is higher, the joint start to separate the system and other factors such as stiffness and weight become more important. Maximum damping does not coincide with the maximum vibrational insertion loss. In order to achieve best vibro-acoustic performance and structure integrity, it is better to use different joint techniques in different frequency bands, since the insertion loss is frequency dependent.

  • 6.
    Feng, Leiping
    et al.
    KTH, Superseded Departments, Vehicle Engineering.
    Liu, M. H.
    Nilsson, A.
    Experimental study of structure-borne sound transmission loss of mechanical joints2001In: Journal of the Acoustical Society of America, ISSN 0001-4966, E-ISSN 1520-8524, Vol. 110, no 3, p. 1391-1397Article in journal (Refereed)
    Abstract [en]

    A mechanical joint is one of the most effective ways to reduce the transmission of structure-borne sound. In order to increase the transmission loss, heavily damped joints are often used, which, in many cases, will reduce the structure integrity and hence can only be used in limited cases. In this study attention is focused on a type of resonant joint, i.e., a joint which will increase the transmission loss but will not reduce the structure integrity. The study is based on experiments in a one-dimensional structure. It is found that by adjusting the overlap of the joint, the transmission loss of 30 dB can be obtained at a certain frequency range without adding any dissipative materials. The mechanism of this high transmission loss is the cantilever-type resonance. The resonant frequency can be predicted precisely. The influence of extra dissipative material is investigated. The performance of the same joint in a finite structure is also examined by using the concept of vibrational insertion loss. When there is a certain damping in a finite system, a rather high insertion loss can still be achieved by using the above-mentioned joint, but the resonant frequency is shifted to higher end. It seems that the effective length of the cantilever is shortened by the finiteness.

  • 7.
    Feng, Leiping
    et al.
    KTH, Superseded Departments, Vehicle Engineering.
    Nilsson, A.
    KTH, Superseded Departments, Vehicle Engineering.
    Kari, Leif
    KTH, Superseded Departments, Vehicle Engineering.
    New designs of sandwich engine foundations1998In: International Conference on Sandwich Construction, 1998, p. 289-300Conference paper (Refereed)
  • 8.
    Feng, Leiping
    et al.
    KTH, Superseded Departments, Vehicle Engineering.
    Nilsson, A.
    KTH, Superseded Departments, Vehicle Engineering.
    Kari, Leif
    KTH, Superseded Departments, Vehicle Engineering.
    Vibration of engine foundations1997In: Modern Practice in Stress and Vibration Analysis / [ed] M D Gilchrist, Rotterdam: Balkema, 1997, p. 311-316Conference paper (Refereed)
  • 9.
    Feng, Leping
    KTH, Superseded Departments, Vehicle Engineering.
    A modified honeycomb panel to increase sound transmission loss2003In: Proceedings of the Tenth International Congress on Sound and Vibration:  , 2003, p. 4549-4554Conference paper (Refereed)
    Abstract [en]

    Honeycomb panels are widely used in aviation industry because of the properties of lightweight and high bending stiffness. However, the sound transmission loss of the panel is often low since the coincident frequency of the panel usually lies below 2 kHz. Previous results show that a single-faced honeycomb panel may acoustically perform much better, especially when it is combined with absorptive materials. This idea is further developed to overcome drawbacks. An improved concept of honeycomb panel is presented, which keeps the basic properties of a honeycomb panel, while the coincident phenomenon in audible frequency is avoided. The theoretical consideration behind this design is discussed. The idea is then tested experimentally. The weighted apparent sound reduction index of the modified honeycomb panel is 4 dB higher than an ordinary honeycomb panel with similar surface density.

  • 10.
    Feng, Leping
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, MWL Structural and vibroacoustics.
    Acoustic models of axial and centrifugal fans for NST technology2003In: Euronoise 2003, Naples, Italy, 2003Conference paper (Refereed)
  • 11.
    Feng, Leping
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, MWL Structural and vibroacoustics.
    Acoustic properties of fluid-filled elastic pipes1994In: Journal of Sound and Vibration, ISSN 0022-460X, E-ISSN 1095-8568, Vol. 176, no 3, p. 399-413Article in journal (Refereed)
  • 12.
    Feng, Leping
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, MWL Structural and vibroacoustics.
    Acoustical Measurements2007Report (Other academic)
  • 13.
    Feng, Leping
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, MWL Structural and vibroacoustics.
    Active control of structurally radiated sound using multi-actuator method1995In: Journal of the Acoustical Society of America, ISSN 0001-4966, E-ISSN 1520-8524, Vol. 98, no 1, p. 397-402Article in journal (Refereed)
  • 14.
    Feng, Leping
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, MWL Structural and vibroacoustics.
    Comparison of different methods for surface impedance and transmission loss measurements in duct2008In: Inter-noise 2008, Shanghai, China, 2008Conference paper (Refereed)
  • 15.
    Feng, Leping
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, MWL Structural and vibroacoustics.
    Experimental studies of the acoustic behaviour of a finite pipe filled with/without fluid1996In: Journal of Sound and Vibration, ISSN 0022-460X, E-ISSN 1095-8568, Vol. 189, no 4, p. 511-524Article in journal (Refereed)
  • 16.
    Feng, Leping
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, MWL Structural and vibroacoustics.
    Influence of compartment size on radiated sound power level of a centrifugal fan2001In: 17th International Congress on Acoustics, Rome, Italy, 2001Conference paper (Refereed)
  • 17.
    Feng, Leping
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, MWL Structural and vibroacoustics.
    Influence of structural damping on sound radiation from a point-excited beam2007In: Turkish Acoustical Society - 36th International Congress and Exhibition on Noise Control Engineering, INTER-NOISE 2007 ISTANBUL, 2007, p. 967-975Conference paper (Refereed)
    Abstract [en]

    The track is the main noise source of a railway when the frequency is below about 1250 Hz. Quite a few efforts have been made to increase the attenuation of the railway track in order to reduce the radiated sound. The attempt of this paper is to investigate the influence of the structural damping on the sound pressure level at the area close to the excitation point instead of the total radiated sound power. For this purpose, the simplest model, i.e. an infinite beam, is adapted. Both near field solution and the propagating wave are included. Results show that when the sound pressure levels at a certain areas close to the excitation is concerned only, the influence of the structural damping is somewhat lower than what expected on the total sound power, partly due to the contribution of the near field solution and partly due to the wave propagation. If the area concerned is small, this influence is also dependent on frequency, because of the length of the bending wave. It is difficult to estimate the influence of the structural damping on wayside noise from laboratory tests with a short track and a point excitation.

  • 18.
    Feng, Leping
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Marcus Wallenberg Laboratory MWL.
    Modified impedance tube measurements and energy dissipation inside absorptive materials2013In: Applied Acoustics, ISSN 0003-682X, E-ISSN 1872-910X, Vol. 71, no 12, p. 1480-1485Article in journal (Refereed)
    Abstract [en]

    Impedance tube is an important tool to measure acoustic properties of a material, for which two methods have been standardized. The methods for a "modified" impedance tube have been developed recently to measure material properties in the condition of an anechoic termination. Instead of commonly used two-load or two-source methods, a method with direct and inverted configuration in cooperation with the single-microphone method is suggested in this paper. With the help of transfer matrix method, combined effect of several materials placed in series can be predicted from individual properties. A simple recurrence formula is obtained to relate the acoustic properties of a multilayer structure with the reflection and transmission coefficients of each layer. Very good agreements are obtained between the prediction and the direct measurements. Energy dissipations inside porous materials for different situations are studied and compared.

  • 19.
    Feng, Leping
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, MWL Structural and vibroacoustics.
    Noise and vibration of fluid-filled elastic pipe coated with an absorptive layer on the inner side of the wall1995In: Journal of Sound and Vibration, ISSN 0022-460X, E-ISSN 1095-8568, Vol. 183, no 1, p. 169-178Article in journal (Refereed)
  • 20.
    Feng, Leping
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, MWL Structural and vibroacoustics.
    Prediction of sound pressure levels from an air-handling unit using Noise Synthesis Technology2002In: The 9th International Congress on Sound and Vibration, Orlando, Florida, USA, 2002Conference paper (Refereed)
  • 21.
    Feng, Leping
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, MWL Structural and vibroacoustics.
    Some aspects on sound transmission loss of finite curved structures with or without pressure difference at the two sides2006In: National congress of the acoustical society of China, Xiamen, China, 2006Conference paper (Refereed)
  • 22.
    Feng, Leping
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, MWL Structural and vibroacoustics.
    Tone-like signal in the wind-induced noise of perforated plates2012In: Acta Acoustica united with Acustica, ISSN 1610-1928, E-ISSN 1861-9959, Vol. 98, no 1, p. 188-194Article in journal (Refereed)
    Abstract [en]

    In some special situations the wind-induced noise of perforated plates may show strong power enhancement in a certain frequency band and hence exhibits a "tone-like" character. This problem is investigated experimentally in laboratory and some test results are presented in this paper. It is shown that the "tone-like" phenomenon happens only when the incident angle of the wind is relatively large to the perforated panel; say between 60 and 80 degrees. There seems an "optimum" wind speed corresponding to the size of the holes for this phenomenon. The peak frequency of the tone-like signal is mainly determined by the thickness of the plate and the size of the holes and can be roughly estimated from the geometry of the plate and the wind speed. The condition when the tone-like phenomenon may happen seems very much dependent on the perforation pattern along the wind direction. Same perforated plate may produce totally different sound in the same wind condition if the orientation of the plate is changed. Randomized hole size and distribution may help to reduce the tone-like signal and hence the total wind-induced noise. Possible explanations of the phenomenon are discussed.

  • 23.
    Feng, Leping
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, MWL Structural and vibroacoustics.
    Vibration reduction by structure modification2001In: : The 8th International Congress on Sound and Vibration, Hong Kong, China, 2001Conference paper (Refereed)
  • 24.
    Feng, Leping
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering.
    Henriksson, Mats
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering. Scania CV, Transmission Development, Sweden.
    Pärsinnen, Mikael
    On model of gearbox noise and dynamic transmission error2005In: Twelfth International Congresson Sound and Vibration, 2005, p. 3198-3205Conference paper (Refereed)
    Abstract [en]

    Gearbox is an important noise source in automotive industry. Dynamic Transmission Error(DTE) describes the dynamic behaviour of the complete gear system and is closely related tothe vibrations of, and hence the noise radiated from, a gearbox. The coherence between DTEand noise radiated has been investigated previously and promising results have been obtained.The paper focuses on the models of DTE and the gearbox noise and the relation betweenthem. In order to understand the behaviour of the signals, a simple model is drawn whereDTE is modelled as the excitation source of a gear system. When the speed of rotation is notextremely high, DTE is expected to be independent of the speed of rotation when theobservation points are located on the wheel. On the other hand, the radiated sound isexpected to increase at the rate of 6 dB per double of the rotation speed, although a bigfluctuation is also expected due to the influence of the shifted frequency and hence thedifferent transfer function. Experimental data is analysed. The dynamic transmission errormeasured on a truck gearbox is separated into deterministic parts and a stochastic part. Theapplied torque has little influence on the averaged DTE of the whole gear because of the highstiffness. However, when the averaged DTE of a single tooth is concerned, the influence ofthe applied torque is rather obvious. The predicted trend of the radiated sound pressure isalso seen in the measured data.

  • 25.
    Feng, Leping
    et al.
    KTH, Superseded Departments, Vehicle Engineering.
    Liu, B.
    On low frequency sound insulation of lightweight structures2004In: Proceedings of the Eleventh International Congress on Sound and Vibration, 2004, p. 2425-2432Conference paper (Refereed)
  • 26.
    Feng, Leping
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, MWL Structural and vibroacoustics.
    Nilsson, Anders
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, MWL Structural and vibroacoustics.
    A new design of lightweight panel to improve both static strength and sound insulation2000In: Inter-noise 2000, Nice, France, 2000Conference paper (Refereed)
  • 27.
    Feng, Leping
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, MWL Structural and vibroacoustics.
    Nilsson, Anders
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, MWL Structural and vibroacoustics.
    Characterization methods and ranking of mechanical joints2000In: ISMA 25, Louven, Belgium, 2000Conference paper (Refereed)
  • 28.
    Feng, Leping
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, MWL Structural and vibroacoustics.
    Nilsson, Anders
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, MWL Structural and vibroacoustics.
    Carniel, X.
    Comparative performance of structural joints and mechanical assemblies2001In: First European Forum Materials and Products for Noise and Vibration Control in Machinery and Transportation Senlis, France, 2001Conference paper (Refereed)
  • 29.
    Feng, Leping
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering.
    Orrenius, Ulf
    Almgren, Martin
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering.
    Jiang, Yan
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering.
    Influence of structural damping on radiation efficiency of a mechanically or acoustically excited panel2006Conference paper (Refereed)
    Abstract [en]

    Previous investigations have shown that damping is a good way to reduce structural vibration, but less effective for sound problems, since the radiation efficiency might be increased dramatically. This problem is further investigated in this paper. Results show that when a constrained damping layer is applied and when mechanical excitation is used, the radiation efficiency is increased by about 9-12 dB. This is mainly due to the near-field radiation around the excitation point, which is more important for a heavily damped structure than for a structure with little damping. The radiation efficiency of an acoustically excited panel, which is directly related to sound transmission, is also increased by about 6-9 dB when damping is added. Instead of radiation from near-field, forced transmission is now the main reason. Although resonant modes, which are the main contributors for vibration, are reduced greatly by added damping, the responses far away from the resonant frequency are little influenced, which are the main contributors for sound radiation and transmission.

  • 30.
    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.

  • 31.
    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.

  • 32.
    Feng, Leping
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Marcus Wallenberg Laboratory MWL.
    Åbom, Mats
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Marcus Wallenberg Laboratory MWL.
    Orrenius, Ulf
    Engineering methods to predict noise levels at reference points with known source properties2015In: Applied Acoustics, ISSN 0003-682X, E-ISSN 1872-910X, Vol. 96, p. 68-74Article in journal (Refereed)
    Abstract [en]

    Two engineering methods are proposed to predict the sound pressure levels at a given point when the sound power level of a noise source is known and the transfer function between the source and the reference point can be obtained. The first method is applicable when the source is surrounded by many reflectors, or inside a box-like structure. A single monopole with average transfer function is suggested for this situation. For a source with a strong directivity placed in an essentially free space, the "box-source" method is recommended to take into account of the source directivity. The total sound power is in this case divided into five independent noise sources which are obtained via ordinary sound power measurement methods. Experimental verifications are made for several cases in laboratory. Satisfactory results are obtained for both methods.

  • 33. Gavric, L.
    et al.
    Calsson, Ulf
    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.
    Measurement of structural intensity using a normal mode approach1997In: Journal of Sound and Vibration, ISSN 0022-460X, E-ISSN 1095-8568, Vol. 206, no 1, p. 81-101Article in journal (Refereed)
  • 34.
    Henriksson, Mats
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering.
    Feng, Lei Peng
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering.
    A dynamic gear model including transmission error and shuttling forcesIn: Journal of mechanical design (1990), ISSN 1050-0472, E-ISSN 1528-9001Article in journal (Other academic)
  • 35.
    Henriksson, Mats
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering.
    Feng, Leping
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering.
    On Shuttling Forces and Transmission Error as Gear Noise ExcitationIn: Journal of mechanical design (1990), ISSN 1050-0472, E-ISSN 1528-9001Article in journal (Other academic)
    Abstract [en]

    This work studies the influence of shuttling forces on gear dynamics. Dependingon the frequency range of interest, shuttling forces can induce bearing forces of thesame order of magnitude as transmission error. A dynamic model including shuttlingforces is presented and the perturbation method in the order domain is used to solvethe equations of motions. The result of the dynamic model is compared with static calculations using a commercial finite element program.

  • 36.
    Henriksson, Mats
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering.
    Feng, Leping
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering.
    Pang, Yuet-Yan
    On Transmission Error, Shuttling Forces and Friction Forces as Gear Noise ExcitationIn: International Journal of Acoustics and Vibration, ISSN 1027-5851Article in journal (Other academic)
    Abstract [en]

    Traditionally, transmission error (TE) has been used to asses the noise propertiesof gears. Measurements of gear noise for a complete truck gearbox have been used tocorrelate noise from a gear pair with calculated static transmission error, shuttling forceand friction forces. Two gear pairs with very similar macro geometry but differentmicro geometry was used. The measurement results show that there is a limitationif transmission error is considered as the only excitation mechanism when designingquiet gears. Often TE is multiplied with the gear mesh stiffness in order to calculatean excitation force. For gear not operating above the critical gear mesh resonance,this often overestimates the importance of TE, thus underestimating the importance ofother sources such as shuttling and friction forces.

  • 37.
    Jiang, Yan
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, MWL Flow acoustics.
    Åbom, Mats
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, MWL Flow acoustics.
    Feng, Leping
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, MWL Structural and vibroacoustics.
    Timouchev, S
    Maliczak, C
    Investigation of sound generation from an axial fan for engine cooling2007In:  , 2007Conference paper (Refereed)
  • 38.
    Kari, Leif
    et al.
    KTH, Superseded Departments, Vehicle Engineering.
    Lindgren, K.
    KTH, Superseded Departments, Vehicle Engineering.
    Feng, Leiping
    KTH, Superseded Departments, Vehicle Engineering.
    Nilsson, A.
    KTH, Superseded Departments, Vehicle Engineering.
    Constrained polymer layers to reduce noise: reality or fiction? - An experimental inquiry into their effectiveness2002In: Polymer testing, ISSN 0142-9418, E-ISSN 1873-2348, Vol. 21, no 8, p. 949-958Article in journal (Refereed)
    Abstract [en]

    The frequency and temperature dependent noise radiation properties of constrained polymer layered oil pans are examined through mobility and intensity measurements. Four metal/polymer/metal sandwich composites of varied thermo-plastic elastomer systems of polystyrene-polybutadiene-polystyrene triblock copolymers are investigated within a wide frequency range covering 1000-5000 Hz, and over a wide temperature range covering 20-100 degreesC, with results compared to those of an ordinary steel oil pan. The mobility and intensity are found to be strongly frequency and temperature dependent, displaying a substantial mobility reduction as compared to that of the ordinary pan, while using the constrained layer damping configurations at their maximum loss factor temperatures. However, the reduction of noise radiation is smaller than that of the mobility at those temperatures, mainly due to the increased radiation efficiency while adding damping materials.

  • 39. Kumar, Sathish
    et al.
    Feng, Leping
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering.
    Orrenius, Ulf
    Sound Transmission Through Double Leaf Partitions: A Criterion for Quick Convergence Using Space Harmonic Analysis2016In: Journal of Vibration and Acoustics-Transactions of the ASME, ISSN 1048-9002, E-ISSN 1528-8927, Vol. 138, no 4, article id 044502Article in journal (Refereed)
    Abstract [en]

    Space harmonic expansion has been used successfully to model sound transmission through infinite, periodically rib-stiffened double leaf partitions. Since the solution to this method is obtained in a series form, computational accuracy needs to be balanced with computational cost as calculation time increases with the number of space harmonic terms. The aim of this article is to provide a criterion to decrease the computational time when using space harmonic analysis. The new criterion helps to select the appropriate space harmonics to be included in the solution based on frequency and the angle of incidence of sound waves. The results are verified by comparing with experimental data available in the literature. For the partition investigated, the computational time is reduced by a factor of ten without compromising the accuracy of the result.

  • 40. Liu, B.
    et al.
    Feng, Leping
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Marcus Wallenberg Laboratory MWL.
    Radiation efficiency of acoustic-excited plates with stringer attachments2007In: 14th International Congress on Sound and Vibration 2007, ICSV 2007, 2007, p. 3782-3789Conference paper (Refereed)
    Abstract [en]

    The average radiation efficiency of acoustic-excited plate with stringer attachments is investigated by using a modal expansion method. This work is an extension to author's previous publication (JSV 2007), where the predicted and measured sound transmission loss for curved aircraft panels was reported. For the plate and frequency range studied here, numerical results reveal that the radiation efficiency of acoustic-excited plate is very sensitive to the damping of the structure. Increasing the structure loss factor significantly increases radiation efficiency far below the plate critical frequency.

  • 41. Liu, B.
    et al.
    Feng, Leping
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, MWL Structural and vibroacoustics.
    Nilsson, A.
    Aversano, M.
    Predicted and measured plate velocities induced by turbulent boundary layers2012In: Journal of Sound and Vibration, ISSN 0022-460X, E-ISSN 1095-8568, Vol. 331, no 24, p. 5309-5325Article in journal (Refereed)
    Abstract [en]

    A method for the prediction of velocity levels of a fuselage plate excited by turbulent boundary layers is described. The aim is to identify a method for the prediction of the relative changes of the velocity levels caused by variations of plate geometry and flight conditions. The Corcos, Efimtsov and Chase models are used to characterize the dynamic surface pressure cross-spectra. Predicted results using these models are compared with the result of in-flight measurements of plate velocities. It is found that the Corcos model gives the best agreement with the measured results for three different flight conditions. The Efimtsov extension and Chase models tend to underestimate the plate response in the lower frequency range. It is evident that the velocity level of the plate elements of the fuselage very much depends on the speed of the aircraft. An increase of the speed of the aircraft by 10% is likely to increase the plate velocity level by 3 dB and a reduction of the speed by 10% would give a reduction of 3 dB.

  • 42.
    Liu, Bilong
    et al.
    KTH, Superseded Departments, Aeronautical and Vehicle Engineering.
    Feng, Leping
    KTH, Superseded Departments, Aeronautical and Vehicle Engineering.
    Sound transmission through a double walled cylindrical shell2003In: Tenth International Congress on Sound and Vibration, 2003Conference paper (Other academic)
  • 43.
    Liu, Bilong
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering.
    Feng, Leping
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering.
    Nilsson, Anders
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering.
    Influence of baffle size and curvature on sound radiated by vibrating panels2004In: Eleventh International Congress on Sound and Vibration, 2004Conference paper (Other academic)
  • 44.
    Liu, Bilong
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Marcus Wallenberg Laboratory MWL.
    Feng, Leping
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Marcus Wallenberg Laboratory MWL.
    Nilsson, Anders
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Marcus Wallenberg Laboratory MWL.
    Influence of overpressure on sound transmission through curved panels2007In: Journal of Sound and Vibration, ISSN 0022-460X, E-ISSN 1095-8568, Journal of sound and vibration, Vol. 302, no 4-5, p. 760-776Article in journal (Refereed)
    Abstract [en]

    A great deal of recent research related to the aeronautic industry has been devoted to the theoretical study of sound transmission through fuselage structures. However, the literature records few test data with reference to the influence of overpressure on sound transmission. In this article, the airborne sound transmission through curved panels under the condition of overpressure at the concave side has been investigated experimentally and it is shown that experimental results agree well with a theoretical prediction due to an infinite cylindrical shell model at relatively high frequencies. Discrepancies, which occur at lower frequencies, can be explained, inter alia, by the influence of the finite size and attached stiffeners of the panel.At frequencies higher than the corresponding ring frequency for the curved panel, both experimental and theoretical predictions reveal that the overpressure at the concave side tends to reduce the sound transmission loss at the rate of about 0.5dB/10000Pa. While at lower frequencies, say well below the ring frequency, the overpressure may increase or reduce sound transmission loss of a finite panel depending on the shift of resonant frequencies resulting from the overpressure.

  • 45.
    Liu, Bilong
    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.
    Nilsson, Anders
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, MWL Structural and vibroacoustics.
    Influence of pressurization on sound insulation of curved airplane panels2005In: 12th International Congress on Sound and Vibration 2005: ICSV 2005, 2005, p. 4843-4850Conference paper (Refereed)
    Abstract [en]

    he purpose of this paper is to investigate the pressurization effects on sound transmission through airplane panels. The airborne sound transmission through airplane panels under the condition of overpressure at one side has been investigated by measurement. The test results agree well with the theoretic prediction of infinite cylindrical shell model at high frequencies, but have considerable discrepancies at low frequencies, which, however, are ready to be explained by the influence of finiteness and stiffeners of the panel. When the frequency is higher than the ring frequency of curved panel, both test and theoretic prediction reveal that the overpressure under laboratory conditions tends to reduce the sound transmission loss at the rate of about 0.5dB/10000 Pa. while at low frequencies, say below around the ring frequency, the overpressure may increase the sound transmission loss of ring-stiffened panel, the reason of this behavior is resulted from the shift of the resonant frequencies led by the increased in-plane tension.

  • 46.
    Liu, Bilong
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Marcus Wallenberg Laboratory MWL.
    Feng, Leping
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, MWL Structural and vibroacoustics.
    Nilsson, Anders
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Marcus Wallenberg Laboratory MWL.
    Sound transmission through curved aircraft panels with stringers and ring frames attachments2007In: Journal of Sound and Vibration, ISSN 0022-460X, E-ISSN 1095-8568, Journal of sound and vibration, Vol. 300, no 3-5, p. 949-973Article in journal (Refereed)
    Abstract [en]

    A numerical approach based on a receptance method has been developed to evaluate the airborne sound insulation of aircraft panels with stringer and ring frame attachments. Theoretical predictions have been compared with laboratory measurements conducted on both model structures and aircraft panels. Certain parameters were varied in this study to gauge stiffener effects on sound transmission through the panel. For large curved aircraft panels studied here, it was found that the ring frames have little influence on sound transmission loss in the frequency range of interest. However, the stringers may have considerable influence on the sound transmission loss. The stringer improves the sound transmission loss for a curved panel in the vicinity of the ring frequency, but may result in a potential deterioration above this frequency. In addition it was found that the sound transmission loss for the composite skin attached with composite stringers was lower than that of the metallic panel attached with metallic stringers. The results suggest that acoustical optimization design for the stringers is necessary to achieve improved airborne sound insulation for aircraft panels

  • 47.
    Liu, Zibo
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering.
    Feng, Leping
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Marcus Wallenberg Laboratory MWL.
    Rumpler, Romain
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Marcus Wallenberg Laboratory MWL.
    Design of broadband acoustic metamaterials for low-frequency noise insulation2017In: The Journal of the Acoustical Society of America, Acoustical Society of America (ASA), 2017, Vol. 141, no 5, p. 3574-3574Conference paper (Other academic)
    Abstract [en]

    An innovative configuration of an acoustic sandwich structure is proposed in this paper, which uses the locally resonant structures to generate stopbands in desired frequency regions and hence to increase the sound transmission loss of the panel. Effects of different types of resonators, including the mounting techniques, are investigated. The methods to broaden the effective stopbands are discussed. The acoustic properties of the sandwich panel with non-flat laminates are also studied. Numerical analyses show that good results can be obtained when combining the laminate modification with the locally resonantstructure, especially when the stopbands are designed to compensate the corresponding coincidence effects of the sandwich panel. The analysis is based on the Finite Element models constructed in COMSOL. Bloch wave vectors are derived at first Brillouin zone by using wave expansion method. Dispersion relation of the structure is discussed. Experimental validation is planned, and the results will be shown in the conference.

  • 48.
    Liu, Zibo
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Marcus Wallenberg Laboratory MWL.
    Rumpler, Romain
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Marcus Wallenberg Laboratory MWL. KTH, School of Engineering Sciences (SCI), Centres, VinnExcellence Center for ECO2 Vehicle design.
    Feng, Leping
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Marcus Wallenberg Laboratory MWL.
    Broadband locally resonant metamaterial sandwich plate for improved noise insulation in the coincidence region2018In: Composite structures, ISSN 0263-8223, E-ISSN 1879-1085, Vol. 200, p. 165-172Article in journal (Refereed)
    Abstract [en]

    A new design for locally resonant metamaterial sandwich plates is proposed in this paper for noise insulation engineering applications. A systematic method to tune the resonance frequency of local resonators is developed in order to overcome the coincidence phenomenon. This method, based on an impedance approach, additionally explains the ability to overcome the antiresonance associated with these local resonators. The influence of the radiated sound from these local resonators is further investigated with finite element (FE) models, particularly in connection with the sound transmission loss (STL) of the resulting metamaterial sandwich plates. The new sandwich design proposed emerges from these analyses, encapsulating the resonators inside the core material. In addition to overcoming the coincidence effect and limiting the noise radiation by the resonators, the proposed design allows to improve the mass ratio of the metamaterial sandwich structure. This, in turn, enables to broaden the working frequency band independently of the material adopted for the resonator. The proposed metamaterial sandwich plate thus combines improved acoustic insulation properties, while maintaining the lightweight nature of the sandwich plate and its good static properties.

  • 49.
    Liu, Zibo
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Marcus Wallenberg Laboratory MWL.
    Rumpler, Romain
    Feng, Leping
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering.
    Investigation of the sound transmission through a locally resonant metamaterial cylindrical shell in the ring frequency regionIn: Article in journal (Refereed)
  • 50.
    Liu, Zibo
    et al.
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Marcus Wallenberg Laboratory MWL.
    Rumpler, Romain
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Marcus Wallenberg Laboratory MWL. KTH, School of Engineering Sciences (SCI), Centres, VinnExcellence Center for ECO2 Vehicle design.
    Feng, Leping
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Marcus Wallenberg Laboratory MWL.
    Investigation of the sound transmission through a locally resonant metamaterial cylindrical shell in the ring frequency region2019In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 125, no 11, article id 115105Article in journal (Refereed)
    Abstract [en]

    Locally resonant metamaterial flat panels have proved to potentially exhibit extraordinary sound transmission loss properties when the resonance frequency of the resonators is tuned to the coincidence frequency region. Whether this technique is also effective to address the ring frequency effect for curved panels is investigated in this paper. For this purpose, a cylindrical shell, as a representation of curved panels, is studied from a theoretical and numerical point of view, with a specific focus on the transmission loss behaviour around the ring frequency region when the shell is mounted with local resonators. The influence from the resonators is presented and compared with that for a flat panel. An inverse effect of the resonators is observed on the sound transmission loss between the metamaterial cylindrical shell and the metamaterial flat panel when the resonance frequency of the resonators is tuned to be below or above the ring or coincidence frequency, respectively. Rather than the extraordinary improvement observed for the metamaterial flat panel, tuning such conventional resonators to the ring frequency of curved panels generates two side dips despite a sharp improvement at the ring frequency itself. This phenomenon is explained from an effective impedance point of view developed in this paper. The approach proposed and the conclusions provided may subsequently allow for the design of suitable resonators in order to resolve the ring frequency effect for curved panels.

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