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On application of radiation loss factor in the prediction of sound transmission loss of a honeycomb panel
KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, MWL Structural and vibroacoustics.ORCID iD: 0000-0002-9632-8398
KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, MWL Structural and vibroacoustics.
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.

Place, publisher, year, edition, pages
2012. Vol. 17, no 1, 47-51 p.
Keyword [en]
radiation loss factor, sound transmission loss, honeycomb panel, orthotropic panel
National Category
Fluid Mechanics and Acoustics
Identifiers
URN: urn:nbn:se:kth:diva-12926ISI: 000301833500005Scopus ID: 2-s2.0-84860747745OAI: oai:DiVA.org:kth-12926DiVA: diva2:319646
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
In thesis
1. The effects of damping treatment on the sound transmission loss of honeycomb panels
Open this publication in new window or tab >>The effects of damping treatment on the sound transmission loss of honeycomb panels
2010 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

In the industry, all passenger vehicles are treated with damping materials to reduce structure-borne sound. Though these damping materials are effective to attenuate structure-borne sound, they have little or no effect on the air-borne sound transmission.The lack of effective predictive methods for assessing the acoustic effects due to added damping on complex industrial structures leads to excessive use of damping materials.Examples are found in the railway industry where sometimes the damping material applied per carriage is more than one ton. The objective of this thesis is to provide a better understanding of the application of these damping materials in particular when applied to lightweight sandwich panels.

As product development is carried out in a fast pace today, there is a strong need for validated prediction tools to assist in the design process. Sound transmission loss of sandwich plates with isotropic core materials can be accurately predicted by calculating the wave propagation in the structure. A modified wave propagation approach is used to predict the sound transmission loss of sandwich panels with honeycomb cores. The honeycomb panels are treated as being orthotropic and the wave numbers are calculated for the two principle directions. The orthotropic panel theory is used to predict the sound transmission loss of panels. Visco-elastic damping with a constraining layer is applied to these structures and the effect of these damping treatment on the sound transmission loss is studied. Measurements are performed to validate these predictions.

Sound radiated from vibrating structures is of great practical importance.The radiation loss factor represents damping associated with the radiation of sound as a result of the vibrating structure and can be a significant contribution for structures around the critical frequency and for composite structures that are very lightly damped. The influence of the radiation loss factor on the sound reduction index of such structures is also studied.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2010. vii, 30 p.
Series
Trita-AVE, ISSN 1651-7660 ; 2010:21
Keyword
Sandwich Structures, Honeycomb Panels, Sound Transmission, Loss Factor, Damping, Sound Radiation
National Category
Fluid Mechanics and Acoustics
Identifiers
urn:nbn:se:kth:diva-12514 (URN)9789174156034 (ISBN)
Presentation
2010-04-25, MWL sal 74, Teknikringen 8, Stockholm, 13:00 (English)
Opponent
Supervisors
Projects
ECO2-Multifunctional body Panels
Note
QC 20100519Available from: 2010-05-19 Created: 2010-05-03 Last updated: 2011-05-03Bibliographically approved
2. Sound transmission properties of honeycomb panels and double-walled structures
Open this publication in new window or tab >>Sound transmission properties of honeycomb panels and double-walled structures
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:nbn:se:kth:diva-96538 (URN)978-91-7501-334-3 (ISBN)
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

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