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Sound transmission through curved aircraft panels with stringers and ring frames attachments
KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Marcus Wallenberg Laboratory MWL.
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, Marcus Wallenberg Laboratory MWL.
2007 (English)In: Journal of Sound and Vibration, ISSN 0022-460X, E-ISSN 1095-8568, Journal of sound and vibration, Vol. 300, no 3-5, 949-973 p.Article in journal (Refereed) Published
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

Place, publisher, year, edition, pages
2007. Vol. 300, no 3-5, 949-973 p.
Keyword [en]
Acoustic variables measurement, Aircraft parts and equipment, Numerical methods, Optimization, Sound insulation, Structural panels
National Category
Other Mechanical Engineering
Identifiers
URN: urn:nbn:se:kth:diva-6123DOI: 10.1016/j.jsv.2006.09.008ISI: 000243561200030Scopus ID: 2-s2.0-33845885801OAI: oai:DiVA.org:kth-6123DiVA: diva2:10743
Note
QC 20100908Available from: 2006-09-15 Created: 2006-09-15 Last updated: 2012-03-23Bibliographically approved
In thesis
1. Acoustical Characteristics of Aircraft Panels
Open this publication in new window or tab >>Acoustical Characteristics of Aircraft Panels
2006 (English)Doctoral thesis, comprehensive summary (Other scientific)
Abstract [en]

A deterministic approach based on a modal expansion and modal receptance method has been developed to evaluate the airborne sound insulation of aircraft panels with stringer and ring frame attachments. Furthermore, this method was extended to predict the noise radiation of stiffening panel subjected to TBL excitation. This approach integrates with the fast and accurate methods in evaluating the modal excitation terms and modal radiation efficiency. Based on these advantages, the effects of the curvature, overpressure, stringers, ring frames, hydrodynamic coincidence, composite structures and structural dissipation on the acoustical properties of a typical aircraft panel are able to be investigated efficiently.

Theoretic predictions were compared with laboratory measurements conducted on both model structures and aircraft panels. It was found that a small curvature may result in significant deterioration of the sound transmission loss at frequencies of interest. Unlike a flat uniform panel, the theoretical prediction for curved panels from the infinite model can not provide good agreement with the measurement close to and well below the ring frequency. However, in this frequency range, the finite model has been proved to be applicable

For the large curved airplane 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 sound transmission loss. The stringer improves this for a curved panel around the ring frequency, but it may result in a potential deterioration of the sound transmission loss above the ring frequency. In this study it is evident that the sound transmission loss of the composite skin attached with composite stringers is lower than that of the metallic panel attached with metallic stringers.

At frequencies higher than the corresponding ring frequency of the curved panel, both experiment and theoretical prediction reveal that the overpressure at the concave side tends to reduce the sound transmission loss at the rate of about 0.5dB /10000 Pa. 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 the resonant frequencies resulting from the overpressure.

For TBL excitation, numerical investigation reveals that the panel with the ring frames behaves more like a sub-panel between two frames. Below 500Hz, the ring frames slightly enhance the sound radiation while dramatically increasing it around 1.3kHz. The TBL forcing field excites the same vibration lever for the panel with and without ring frame attachments, but the modes excited for the panel with ring frames radiate more sound. Unlike the ring frames, the stringers increase sound radiation below 1kHz. Above 1kHz, the sub-panels between two bays respond independently and the stringer effects is therefore not obvious.

Place, publisher, year, edition, pages
Stockholm: KTH, 2006. 23 p.
Series
TRITA-AVE, ISSN 1651-7660 ; 2006:60
Keyword
Acoustics, sound transmission loss, stiffener, stiffening, aircraft panel, cylindrical shell, turbulent boundary layer, TBL, noise, sound radiation
National Category
Fluid Mechanics and Acoustics
Identifiers
urn:nbn:se:kth:diva-4102 (URN)
Public defence
2006-09-26, Salongen, KTHB, Osquars Backe 31, Stockholm, 13:00
Opponent
Supervisors
Note

QC 20100908

Available from: 2006-09-15 Created: 2006-09-15 Last updated: 2017-02-23Bibliographically approved
2. Sound transmission through aircraft panels
Open this publication in new window or tab >>Sound transmission through aircraft panels
2005 (English)Licentiate thesis, comprehensive summary (Other scientific)
Place, publisher, year, edition, pages
Stockholm: KTH, 2005. 13 p.
Series
Trita-AVE, ISSN 1651-7660 ; 2005:16
Keyword
sound transmission loss, stiffener, stiffening, aircraft panel, cylindrical shell
National Category
Vehicle Engineering
Identifiers
urn:nbn:se:kth:diva-494 (URN)
Note
QC 20101209Available from: 2005-11-22 Created: 2005-11-22 Last updated: 2011-10-05Bibliographically approved

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