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Sound transmission properties of honeycomb panels and double-walled structures
KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Marcus Wallenberg Laboratory MWL. (Experimental Acoustics)
2012 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

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

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

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

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2012. , xi, 74 p.
Series
Trita-AVE, ISSN 1651-7660 ; 2012:20
National Category
Vehicle Engineering
Identifiers
URN: urn:nbn:se:kth:diva-96538ISBN: 978-91-7501-334-3 (print)OAI: oai:DiVA.org:kth-96538DiVA: diva2:531193
Public defence
2012-06-14, F3, Lindstedtsvägen 26, KTH, Stockholm, 13:00 (English)
Opponent
Supervisors
Funder
TrenOp, Transport Research Environment with Novel Perspectives
Note

QC 20120607

Available from: 2012-06-07 Created: 2012-06-06 Last updated: 2013-04-11Bibliographically approved
List of papers
1. On application of radiation loss factor in the prediction of sound transmission loss of a honeycomb panel
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, 47-51 p.Article 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.

Keyword
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
2. Predicting the sound transmission loss of honeycomb panels using the wave propagation approach
Open this publication in new window or tab >>Predicting the sound transmission loss of honeycomb panels using the wave propagation approach
2011 (English)In: Acta Acoustica united with Acustica, ISSN 1610-1928, E-ISSN 1861-9959, Vol. 97, no 5, 869-876 p.Article in journal (Refereed) Published
Abstract [en]

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

Keyword
Acoustic wave transmission, Anisotropy, Architectural acoustics, Curve fitting, Damping, Honeycomb structures, Orthotropic plates, Resonance, Sandwich structures, Structural dynamics
National Category
Fluid Mechanics and Acoustics
Identifiers
urn:nbn:se:kth:diva-12927 (URN)10.3813/AAA.918466 (DOI)000295114100016 ()2-s2.0-80052447110 (Scopus ID)
Note
QC 20100519 QC 20111017Available from: 2010-05-19 Created: 2010-05-19 Last updated: 2017-12-12Bibliographically approved
3. Modelling the sound transmissionthrough rib-stiffened double-leaf partitions with cavity absorption
Open this publication in new window or tab >>Modelling the sound transmissionthrough rib-stiffened double-leaf partitions with cavity absorption
(English)In: Journal of Sound and Vibration, ISSN 0022-460X, E-ISSN 1095-8568Article in journal (Other academic) Submitted
National Category
Fluid Mechanics and Acoustics
Identifiers
urn:nbn:se:kth:diva-96755 (URN)
Note
QS 2012Available from: 2012-06-11 Created: 2012-06-11 Last updated: 2017-12-07Bibliographically approved
4. Modelling the sound transmission through rib-stiffened sandwich double-leaf partitions using space harmonic analysis
Open this publication in new window or tab >>Modelling the sound transmission through rib-stiffened sandwich double-leaf partitions using space harmonic analysis
(English)In: Journal of Sound and Vibration, ISSN 0022-460X, E-ISSN 1095-8568Article in journal (Other academic) Submitted
National Category
Fluid Mechanics and Acoustics
Identifiers
urn:nbn:se:kth:diva-96756 (URN)
Note
QS 2012Available from: 2012-06-11 Created: 2012-06-11 Last updated: 2017-12-07Bibliographically approved

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