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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: 2018-08-07Bibliographically approved
Liu, Z., Feng, L. & Rumpler, R. (2017). Design of broadband acoustic metamaterials for low-frequency noise insulation. Journal of the Acoustical Society of America, 141(5), 3574-3574
Open this publication in new window or tab >>Design of broadband acoustic metamaterials for low-frequency noise insulation
2017 (English)In: Journal of the Acoustical Society of America, ISSN 0001-4966, E-ISSN 1520-8524, Vol. 141, no 5, p. 3574-3574Article in journal (Refereed) Published
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)
Note

QC 20180507

Available from: 2018-04-30 Created: 2018-04-30 Last updated: 2018-05-24Bibliographically 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
Orrenius, U., Betgen, B., Feng, L., Åbom, M., Iglesias, E. L., Thompson, D. & Brunström, S. (2014). Rail vehicle source assessment within a virtual certification process. In: PROCEEDINGS OF INTERNATIONAL CONFERENCE ON NOISE AND VIBRATION ENGINEERING (ISMA2014) AND INTERNATIONAL CONFERENCE ON UNCERTAINTY IN STRUCTURAL DYNAMICS (USD2014): . Paper presented at International Conference on Noise and Vibration Engineering (ISMA), SEP 15-17, 2014, Leuven, BELGIUM (pp. 3511-3525).
Open this publication in new window or tab >>Rail vehicle source assessment within a virtual certification process
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2014 (English)In: PROCEEDINGS OF INTERNATIONAL CONFERENCE ON NOISE AND VIBRATION ENGINEERING (ISMA2014) AND INTERNATIONAL CONFERENCE ON UNCERTAINTY IN STRUCTURAL DYNAMICS (USD2014), 2014, p. 3511-3525Conference paper, Published paper (Refereed)
Abstract [en]

The present paper aims at giving an overview of the vehicle noise source modelling work carried out within the Acoutrain FP7 European research project. Results are presented for several areas including: equivalent source modelling concept applied to typical train sources, component based models for aero-acoustic noise generation of pantographs and installation effects of bogie and roof mounted sources. A process to characterize vehicle noise sources in an industrial context is presented. It is shown that equivalent monopole models, for which the source is described by a few monopoles, can be applied to represent real vehicle sources. It is also displayed how analytical models can be used to calculate the insertion loss of screens for sources that can be represented by point sources. Ray tracing and energy BEM models are used to determine the high frequency installation effect of a source in the bogie and a practical, procedure for in-situ testing of installation effects is suggested. For high speed applications a component based model is shown to accurately represent the spectrum of a train pantograph. It is concluded that the results to date are promising but more work is needed to validate the proposed process and methods for real vehicle installations in terms of modelling accuracy and usability in a virtual testing framework for TSI certification purposes.

National Category
Engineering and Technology
Identifiers
urn:nbn:se:kth:diva-166528 (URN)000352201004028 ()2-s2.0-84913557629 (Scopus ID)978-90-73802-91-9 (ISBN)
Conference
International Conference on Noise and Vibration Engineering (ISMA), SEP 15-17, 2014, Leuven, BELGIUM
Note

QC 20150512

Available from: 2015-05-12 Created: 2015-05-11 Last updated: 2015-06-04Bibliographically approved
Feng, L. (2013). Modified impedance tube measurements and energy dissipation inside absorptive materials. Applied Acoustics, 71(12), 1480-1485
Open this publication in new window or tab >>Modified impedance tube measurements and energy dissipation inside absorptive materials
2013 (English)In: Applied Acoustics, ISSN 0003-682X, E-ISSN 1872-910X, Vol. 71, no 12, p. 1480-1485Article in journal (Refereed) Published
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.

Keywords
Sound absorption, Impedance tube, Scattering matrix, Transfer matrix method, Direct and inverted configurations
National Category
Engineering and Technology
Identifiers
urn:nbn:se:kth:diva-131223 (URN)10.1016/j.apacoust.2013.06.013 (DOI)000324227100021 ()2-s2.0-84880351638 (Scopus ID)
Note

QC 20131011

Available from: 2013-10-11 Created: 2013-10-10 Last updated: 2017-12-06Bibliographically approved
Mehrgou, M., Jönsson, O. & Feng, L. (2013). On sound power measurement of the engine in anechoic room with imperfections. In: 42nd International Congress and Exposition on Noise Control Engineering 2013, INTER-NOISE 2013: Noise Control for Quality of Life. Paper presented at 42nd International Congress and Exposition on Noise Control Engineering 2013: Noise Control for Quality of Life, INTER-NOISE 2013; Innsbruck; Austria; 15 September 2013 through 18 September 2013 (pp. 4358-4364). OAL-Osterreichischer Arbeitsring fur Larmbekampfung
Open this publication in new window or tab >>On sound power measurement of the engine in anechoic room with imperfections
2013 (English)In: 42nd International Congress and Exposition on Noise Control Engineering 2013, INTER-NOISE 2013: Noise Control for Quality of Life, OAL-Osterreichischer Arbeitsring fur Larmbekampfung , 2013, p. 4358-4364Conference paper, Published paper (Refereed)
Abstract [en]

Engine noise is one of the most critical noises in urban noises. NVH improvements are essential in order to fulfill various noise emission regulations such as ISO 362. Reducing engine noise has become a necessity for engine developers. Measurement plays an important role beside the simulations to improve the NVH behavior, because the engine is a rather complicated mechanical system with many components. ISO 3745 is an ideal method for sound power measurement for internal combustion engines since it provides a fast measurement through many different engine speeds. However room as well as the measurement method, should comply with this standard. Because of the size and installation situation for a running engine there is limited space for measurement; and it is difficult to reach standards requirements especially for such a directive sound source. The difficulty to meet these requirements also applies to Scania's anechoic room. Here engine noise characteristics and the uncertainties in sound power measurement have been discussed based on both measurement and simulation. Recommendation has been made to decrease the uncertainty of sound power measurement.

Place, publisher, year, edition, pages
OAL-Osterreichischer Arbeitsring fur Larmbekampfung, 2013
Keywords
Sound power measurement, IC Engine, Anechoic room
National Category
Other Mechanical Engineering
Identifiers
urn:nbn:se:kth:diva-136779 (URN)2-s2.0-84904489131 (Scopus ID)978-163266267-5 (ISBN)
Conference
42nd International Congress and Exposition on Noise Control Engineering 2013: Noise Control for Quality of Life, INTER-NOISE 2013; Innsbruck; Austria; 15 September 2013 through 18 September 2013
Note

QC 20131219

Available from: 2013-12-09 Created: 2013-12-09 Last updated: 2014-09-15Bibliographically approved
Nilsson, A., Liu, B. & Feng, L. (2013). Prediction of interior noise of a small aircraft. In: 20th International Congress on Sound and Vibration 2013, ICSV 2013: Volume 1, 2013. Paper presented at 20th International Congress on Sound and Vibration 2013, ICSV 2013; Bangkok; Thailand; 7 July 2013 through 11 July 2013 (pp. 411-418). Bangkok, Thailand: The International Institute of Acoustics and Vibration (IIAV)
Open this publication in new window or tab >>Prediction of interior noise of a small aircraft
2013 (English)In: 20th International Congress on Sound and Vibration 2013, ICSV 2013: Volume 1, 2013, Bangkok, Thailand: The International Institute of Acoustics and Vibration (IIAV) , 2013, p. 411-418Conference paper, Published paper (Refereed)
Abstract [en]

The aim was to determine, already at the design stage, the interior noise level in a new small aircraft. The noise predictions were based on full-scale measurements on an existing model. A number of models for the prediction of velocity levels of a fuselage excited by turbulent boundary layers are discussed. Predicted results are compared to the result of in-flight measurements. It is found that the Corcos model gives the best agreement with the measured results. It is found 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 by 10 % increases the plate velocity level by 3 dB. The velocity level is also strongly dependent on the plate thickness. An increase of the thickness by 50 % will decrease the velocity level by 5 dB. Small variations of other parameters like width and height and curvature of plate have only a very marginal effect on the plate velocity in the frequency range of interest. However, the acoustic power radiated into the aircraft cabin depends on the plate velocity of the fuselage as well the sound radiation properties of the plate structure. In the frequency, range of importance for the A-weighted noise level in the cabin the sound radiation ratio is increased as the plate thickness is increased. The noise level in the cabin is thus reduced much less than the velocity level of the fuselage by increasing the plate thickness. An increase of the width and length of plate elements reduces the sound intensity radiated by a plate. A combination of increased width and length and thickness of plate can result in a reduced noise radiation from the fuselage and thus in a reduced interior noise level.

Place, publisher, year, edition, pages
Bangkok, Thailand: The International Institute of Acoustics and Vibration (IIAV), 2013
Keywords
Acoustic generators, Acoustic noise, Acoustic noise measurement, Acoustic properties, Acoustic wave propagation, Acoustic wave scattering, Cabins (aircraft), Velocity
National Category
Engineering and Technology
Identifiers
urn:nbn:se:kth:diva-136776 (URN)2-s2.0-84897107182 (Scopus ID)
Conference
20th International Congress on Sound and Vibration 2013, ICSV 2013; Bangkok; Thailand; 7 July 2013 through 11 July 2013
Note

QC 20140102

Available from: 2013-12-09 Created: 2013-12-09 Last updated: 2014-06-26Bibliographically approved
Feng, L. & Ramanathan, S. K. (2012). On application of radiation loss factor in the prediction of sound transmission loss of a honeycomb panel. International Journal of Acoustics and Vibration, 17(1), 47-51
Open this publication in new window or tab >>On application of radiation loss factor in the prediction of sound transmission loss of a honeycomb panel
2012 (English)In: International Journal of Acoustics and Vibration, ISSN 1027-5851, Vol. 17, no 1, p. 47-51Article in journal (Refereed) Published
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.

Keywords
radiation loss factor, sound transmission loss, honeycomb panel, orthotropic panel
National Category
Fluid Mechanics and Acoustics
Identifiers
urn:nbn:se:kth:diva-12926 (URN)000301833500005 ()2-s2.0-84860747745 (Scopus ID)
Funder
TrenOp, Transport Research Environment with Novel Perspectives
Note

QC 20120801

Available from: 2010-05-19 Created: 2010-05-19 Last updated: 2017-12-12Bibliographically approved
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Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0002-9632-8398

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