However the major challenge in the present study was to incorporate the mechanical link of finite stiffness in the modal coupling of the two plates. Results are compared with a full transient analysis of the complete system and it is observed that they are in very good agreement. Modal analysis is performed in an ANSYS environment and the modal parameters are exported to a MATLAB environment where the analysis is carried out to obtain the transmission characteristics of the double wall. The analysis domain in terms of frequency range was limited to 0 – 500 Hz.
Two different separation thicknesses/gaps of 0.1 m and 0.05 m are taken into consideration to model the acoustic domain. The two structural panels considered for this study are of size 0.5 m x 0.35 m x 0.002 m and 0.5 m x 0.35 m x 0.003 m, respectively. In the present study an attempt is made to model the sound transmission behaviour through a finite double wall panel using a modal approach wherein the in-vacuo structural modes and rigid wall acoustic modes are coupled using Green’s Theorem. The studies are also limited to simplified structural forms and boundary conditions. In the literatures available so far most of the noise transmission studies through double wall do not include the mechanical connectors. Although they are very efficient in reducing the acoustic radiation in general, they have a problem of mass-air-mass coupling in the vicinity of which the noise transmission is highly magnified, Furthermore, the two panels forming the double wall need to be mechanically connected which forms a path of acoustic transfer too. Effect of the thickness of the air gap between the two curved surfaces on the sound power radiation has also been noted.ĭouble wall panels with two structural leaves and air in between them form an integral part ofĪircraft fuselage, automobile bodies, glazed doors and windows in buildings etc. It has been observed in the present study that the radius of curvature of the surface has a prominent effect on the behavior of radiated sound power into the free field. The developed model is first validated with various numerical models available. An elemental radiator approach is implemented to calculate the radiated energy from the curved surface in to the free field. A modal expansion theory based on Green׳s theorem is implemented to model the energy transmission through an acoustically coupled double-wall curved panel.
In the developed model to simulate a stiffened aircraft fuselage configuration, the outer wall is provided with longitudinal stiffeners. Subsequently the radiation of sound power into the free field from the curved panel in the low to mid frequency range is also studied.
In this quest, the present work tries to delve into the modeling of energy transmission through a double-wall curved panel. However, the scientific community is yet to develop a reliable prediction method for a suitable vibro-acoustic model for sound transmission through a curved double-wall panel.
It is a common practice in aerospace and automobile industries to use double wall panels as fuselage skins or in window panels to improve acoustic insulation.
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