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Publications (10 of 65) Show all publications
Feng, L. (2019). Enhancement of low frequency sound absorption by placing thin plates on surface or between layers of porous materials. Journal of the Acoustical Society of America, 146(2), EL141-EL144
Open this publication in new window or tab >>Enhancement of low frequency sound absorption by placing thin plates on surface or between layers of porous materials
2019 (English)In: Journal of the Acoustical Society of America, ISSN 0001-4966, E-ISSN 1520-8524, Vol. 146, no 2, p. EL141-EL144Article in journal (Refereed) Published
Abstract [en]

Rigid thin plates can be used, either on the surface or between layers of materials, to improve the sound absorption properties of porous materials at low frequencies, especially for materials with low sound absorption. Measurement results obtained from a 100mm impedance tube, for different combinations of porous materials and thin plates, are supplied. Possible physical explanations are discussed. The size of the plate, together with the original properties of the porous material, determines the useful frequency region of the method. The technique of surface-placed thin plates can be directly applied to existing structures without making any changes of the original system, and the results are comparable to those with more complicated modifications.

Place, publisher, year, edition, pages
ACOUSTICAL SOC AMER AMER INST PHYSICS, 2019
National Category
Fluid Mechanics and Acoustics
Identifiers
urn:nbn:se:kth:diva-260193 (URN)10.1121/1.5121571 (DOI)000483887400010 ()31472554 (PubMedID)2-s2.0-85070565374 (Scopus ID)
Note

QC 20190930

Available from: 2019-09-30 Created: 2019-09-30 Last updated: 2019-09-30Bibliographically approved
Liu, Z., Rumpler, R. & Feng, L. (2019). Investigation of the sound transmission through a locally resonant metamaterial cylindrical shell in the ring frequency region. Journal of Applied Physics, 125(11), Article ID 115105.
Open this publication in new window or tab >>Investigation of the sound transmission through a locally resonant metamaterial cylindrical shell in the ring frequency region
2019 (English)In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 125, no 11, article id 115105Article in journal (Refereed) Published
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.

Place, publisher, year, edition, pages
American Institute of Physics (AIP), 2019
National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-249881 (URN)10.1063/1.5081134 (DOI)000462014300023 ()2-s2.0-85063319719 (Scopus ID)
Note

QC 20190424

Available from: 2019-04-24 Created: 2019-04-24 Last updated: 2019-04-24Bibliographically approved
Song, Y., Feng, L., Liu, Z., Wen, J. & Yu, D. (2019). Suppression of the vibration and sound radiation of a sandwich plate via periodic design. International Journal of Mechanical Sciences, 150, 744-754
Open this publication in new window or tab >>Suppression of the vibration and sound radiation of a sandwich plate via periodic design
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2019 (English)In: International Journal of Mechanical Sciences, ISSN 0020-7403, E-ISSN 1879-2162, Vol. 150, p. 744-754Article in journal (Refereed) Published
Abstract [en]

This paper investigates the suppression of vibration and sound radiation of a sandwich plate through the use of periodic design. A periodic sandwich plate is constructed and its dispersion relation is calculated. The vibration and sound radiation properties of the periodic sandwich plate are studied. Via the comparison of the periodic and bare sandwich plate, the effects of the periodic design on the vibration and sound radiation are analysed. Further, to know the sound radiation properties better, sound radiation efficiency of the periodic and bare sandwich plates is compared. In addition, the effects of the boundary conditions on the properties of the periodic sandwich plate are analysed. The numerical results demonstrate that the vibration and sound radiation are greatly suppressed over the stop band of the periodic sandwich plate. The suppression can also be obtained in part of pass bands. It is also shown that the periodic design can be an effective method for the reduction of the sound radiation efficiency. The suppression for the vibration and sound is greater than that caused by only increasing the mass of the plate in the designing frequency range.

Place, publisher, year, edition, pages
Elsevier, 2019
National Category
Fluid Mechanics and Acoustics
Identifiers
urn:nbn:se:kth:diva-244465 (URN)10.1016/j.ijmecsci.2018.10.055 (DOI)000458597800064 ()2-s2.0-85056234548 (Scopus ID)
Note

QC 20190305

Available from: 2019-02-21 Created: 2019-02-21 Last updated: 2019-03-08Bibliographically approved
Liu, Z., Rumpler, R. & Feng, L. (2018). Broadband locally resonant metamaterial sandwich plate for improved noise insulation in the coincidence region. Composite structures, 200, 165-172
Open this publication in new window or tab >>Broadband locally resonant metamaterial sandwich plate for improved noise insulation in the coincidence region
2018 (English)In: Composite structures, ISSN 0263-8223, E-ISSN 1879-1085, Vol. 200, p. 165-172Article in journal (Refereed) Published
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.

Place, publisher, year, edition, pages
Elsevier, 2018
Keywords
Acoustic metamaterial, Sandwich plate, Sound transmission loss, Coincidence frequency
National Category
Materials Engineering
Identifiers
urn:nbn:se:kth:diva-232743 (URN)10.1016/j.compstruct.2018.05.033 (DOI)000439466100016 ()2-s2.0-85047501239 (Scopus ID)
Funder
Swedish Research Council, 2015-04925VINNOVA, 2016-05195
Note

QC 20180807

Available from: 2018-08-07 Created: 2018-08-07 Last updated: 2019-03-08Bibliographically approved
Piana, E. A., Carlsson, U. & Feng, L. (2018). Determination and optimisation of the sound reduction index of ship bulkheads through the wave propagation approach. In: Proceedings of ISMA 2018 - International Conference on Noise and Vibration Engineering and USD 2018 - International Conference on Uncertainty in Structural Dynamics: . Paper presented at 28th International Conference on Noise and Vibration Engineering, ISMA 2018 and 7th International Conference on Uncertainty in Structural Dynamics, USD 2018; Leuven; Belgium; 17 September 2018 through 19 September 2018 (pp. 4527-4541). KU Leuven - Departement Werktuigkunde
Open this publication in new window or tab >>Determination and optimisation of the sound reduction index of ship bulkheads through the wave propagation approach
2018 (English)In: Proceedings of ISMA 2018 - International Conference on Noise and Vibration Engineering and USD 2018 - International Conference on Uncertainty in Structural Dynamics, KU Leuven - Departement Werktuigkunde , 2018, p. 4527-4541Conference paper, Published paper (Refereed)
Abstract [en]

Lightweight composite structures are progressively replacing traditional materials like steel structures in the shipbuilding industry for their light weight and good mechanical characteristics. However, a lightweight composite structure has generally poor acoustic properties and is not suitable to shield noise. In this case some comfort issues may arise on board. Ships are also a source of underwater noise, which can seriously pollute the aquatic environment if a suitable form of shielding is not envisaged. It is therefore essential that some acoustic features are predicted and optimised. The paper presents the measurements carried out on two different types of bulkhead: a homogeneous ribbed fibreglass partition and a sandwich structure with two symmetrical fibreglass leaves plus a balsa core. The optimisation of such structures can be carried out following the simulations performed by using a code based on the wave propagation approach theory.

Place, publisher, year, edition, pages
KU Leuven - Departement Werktuigkunde, 2018
National Category
Other Engineering and Technologies
Identifiers
urn:nbn:se:kth:diva-246511 (URN)2-s2.0-85060385040 (Scopus ID)9789073802995 (ISBN)
Conference
28th International Conference on Noise and Vibration Engineering, ISMA 2018 and 7th International Conference on Uncertainty in Structural Dynamics, USD 2018; Leuven; Belgium; 17 September 2018 through 19 September 2018
Note

QC 20190326

Available from: 2019-03-26 Created: 2019-03-26 Last updated: 2019-03-26Bibliographically approved
Liu, Z., Rumpler, R. & Feng, L. (2018). Investigation on the acoustic behaviour of a locally resonant metamaterial curved panel. In: : Hiroshima Calling, ICSV 2018. Paper presented at 25th International Congress on Sound and Vibration 2018 (pp. 3409-3416). Hiroshima, 6
Open this publication in new window or tab >>Investigation on the acoustic behaviour of a locally resonant metamaterial curved panel
2018 (English)In: : Hiroshima Calling, ICSV 2018, Hiroshima, 2018, Vol. 6, p. 3409-3416Conference paper, Oral presentation with published abstract (Other academic)
Abstract [en]

In order to seek for new ways to improve the sound transmission loss at ring frequency range for curved aeronautical structures, a semi-infinite curved panel, representing aircraft fuselage, is studied in this research. First, a minor modification on Koval's classical theory for cylindrical shells is made to incorporate effective mass theory for acoustic metamaterials. Then, based on the finite element simulations, the possibility of improving the acoustic behaviour of such panels by using locally resonant acoustic metamaterial treatment is investigated. Both the host curved panel, and the host panel periodically mounted with local resonators, denoted as metamaterial curved panel, are compared from the transmission loss point of view. The observations show that the antiresonance dip appears first rather than the resonance peak in the sound transmission loss for the tested metamaterial curved panel, which may be explained by the effective impedance of the panel. The influences of the panel curvature on the dynamic behaviour of the local resonators are further discussed in comparison to the same resonantsystem acting on the flat panel. Both the finite element simulations and the theoretical estimations show the same trend, thus confirms the proposed explanation.

Place, publisher, year, edition, pages
Hiroshima: , 2018
National Category
Vehicle Engineering Fluid Mechanics and Acoustics
Identifiers
urn:nbn:se:kth:diva-244438 (URN)2-s2.0-85058798180 (Scopus ID)
Conference
25th International Congress on Sound and Vibration 2018
Note

QC 20190226

Available from: 2019-02-20 Created: 2019-02-20 Last updated: 2019-02-26Bibliographically approved
Liu, Z., Feng, L. & Rumpler, R. (2017). Design of broadband acoustic metamaterials for low-frequency noise insulation. In: The Journal of the Acoustical Society of America: . Paper presented at 173rd Meeting of Acoustical Society of America and 8th Forum Acusticum (pp. 3574-3574). Acoustical Society of America (ASA), 141(5)
Open this publication in new window or tab >>Design of broadband acoustic metamaterials for low-frequency noise insulation
2017 (English)In: The Journal of the Acoustical Society of America, Acoustical Society of America (ASA), 2017, Vol. 141, no 5, p. 3574-3574Conference paper, Oral presentation with published abstract (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.

Place, publisher, year, edition, pages
Acoustical Society of America (ASA), 2017
National Category
Fluid Mechanics and Acoustics
Identifiers
urn:nbn:se:kth:diva-226991 (URN)10.1121/1.4987600 (DOI)
Conference
173rd Meeting of Acoustical Society of America and 8th Forum Acusticum
Note

QC 20180507

Available from: 2018-04-30 Created: 2018-04-30 Last updated: 2019-02-26Bibliographically approved
Song, Y., Feng, L., Wen, J., Yu, D. & Wen, X. (2015). Analysis and enhancement of flexural wave stop bands in 2D periodic plates. Physics Letters A, 379(22-23)
Open this publication in new window or tab >>Analysis and enhancement of flexural wave stop bands in 2D periodic plates
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2015 (English)In: Physics Letters A, ISSN 0375-9601, E-ISSN 1873-2429, Vol. 379, no 22-23Article in journal (Other academic) Published
Abstract [en]

The band structure and enhancement of flexural wave stop bands in a 2D periodic plate are investigated. A unified method for analysing and designing the stop band of the plates with various attached structures is proposed. The effect of attached structures is considered based on their equivalent parameters (added equivalent mass and equivalent moment of inertia). The influences of the equivalent parameters on the band structures are studied. Three cases are considered: adding pure equivalent mass, pure equivalent moment of inertia and the combination of these two. The stop bands are enhanced via the multi interaction between the host plate and the attached structure. The enhancement pattern is determined, and several ways to obtain a wider combined stop band are presented. The frequency response functions of corresponding finite periodic plates are calculated to verify the stop bands and their enhancement in a number of typical cases.

National Category
Vehicle Engineering
Identifiers
urn:nbn:se:kth:diva-158023 (URN)10.1016/j.physleta.2015.01.037 (DOI)000353613600010 ()2-s2.0-84925843246 (Scopus ID)
Note

Updated from manuscript to article in journal.

QC 20150521

Available from: 2014-12-19 Created: 2014-12-19 Last updated: 2017-12-05Bibliographically approved
Feng, L., Åbom, M. & Orrenius, U. (2015). Engineering methods to predict noise levels at reference points with known source properties. Applied Acoustics, 96, 68-74
Open this publication in new window or tab >>Engineering methods to predict noise levels at reference points with known source properties
2015 (English)In: Applied Acoustics, ISSN 0003-682X, E-ISSN 1872-910X, Vol. 96, p. 68-74Article in journal (Refereed) Published
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.

Keywords
Railway noise, Equivalent monopole, Source directivity, Engineering method, Average transfer function, Directional source model
National Category
Other Engineering and Technologies
Identifiers
urn:nbn:se:kth:diva-169235 (URN)10.1016/j.apacoust.2015.03.014 (DOI)000355033900008 ()2-s2.0-84926058967 (Scopus ID)
Funder
EU, FP7, Seventh Framework Programme, FP7-284877
Note

QC 20150615

Available from: 2015-06-15 Created: 2015-06-12 Last updated: 2017-12-04Bibliographically approved
Song, Y., Feng, L., Wen, J., Yu, D. & Wen, X. (2015). Reduction of the sound transmission of a periodic sandwich plate using the stop band concept. Composite structures, 128, 428-436
Open this publication in new window or tab >>Reduction of the sound transmission of a periodic sandwich plate using the stop band concept
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2015 (English)In: Composite structures, ISSN 0263-8223, E-ISSN 1879-1085, Vol. 128, p. 428-436Article in journal (Refereed) Published
Abstract [en]

The sound transmission of a sandwich plate and its reduction using the stop band concept are investigated in this paper. A periodic sandwich plate consisting of a host plate and the attached structures is designed. The dispersion relation and the stop band of the periodic sandwich plate are studied first. The sound transmission of the periodic and bare sandwich plates is analysed and compared. The reduction from the stop band design (i.e., periodically adding stepped resonators) on the sound transmission of the sandwich plates is studied. The reasons for this reduction are analysed. In addition, the properties of the sandwich plate with different boundary conditions are also briefly studied. The numerical results indicate that the sound transmission is significantly reduced over the stop band of the periodic sandwich plate. The improvement can also exist in the frequency range outside the stop band.

Keywords
Reduction, Sandwich plate, Sound transmission, Stop band, Acoustic wave transmission, Architectural acoustics, Dispersions, Plates (structural components), Different boundary condition, Dispersion relations, Frequency ranges, Numerical results, Sandwich plates, Stop-bands, Periodic structures
National Category
Fluid Mechanics and Acoustics
Identifiers
urn:nbn:se:kth:diva-167684 (URN)10.1016/j.compstruct.2015.02.053 (DOI)000354583300038 ()2-s2.0-84927602969 (Scopus ID)
Note

QC 20150602

Available from: 2015-06-02 Created: 2015-05-22 Last updated: 2017-12-04Bibliographically approved
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0002-9632-8398

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