A Structural Modification Methodology Adapted to a Vibro-Acoustic Model to Improve the Interior Noise

Date

2009-11-26

Author

Özgüven, Hasan Nevzat
Başdoğan , İpek
Canbaloğlu, Güvenç

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The structural-borne noise inside the passenger cabin of automobiles, which is mainly caused by the vibrating panels enclosing the vehicle, dominates the low frequency noise inside the cabin. Excitations coming from the engine cause the panels to vibrate mainly at their resonance frequencies. These vibrating panels cause a change in the sound pressure level (SPL) within the cabin, and consequently, an undesirable booming noise. The SPL can be predicted using a vibro-acoustic model which includes the Finite Element Model (FEM) for the structural analysis of the passenger cabin, and the Boundary Element Model (BEM) for the acoustic analysis of the cavity inside the cabin. The structural design of the panels can be modified (eg: adding a stiffener to the panel, adding or removing mass, etc) to improve the SPL. The modal analysis of the structural model has to be repeated after every modification before the reanalysis of the vibro-acoustic model. However, such changes require considerable computational time especially when the structural models are very complex. In anticipation of these needs, we adapted a methodology that utilizes the frequency response functions (FRFs) of the original model for the reanalysis of the structure that is subjected to structural modification. We used a rectangular box with a very flexible mid-panel to demonstrate the developed methodology. In the presented method, the receptances of the original structure are used together with the dynamic stiffness of the components that are added or removed from the original structure to perform the structural modification and to calculate the receptance matrices of the modified system. Then, the receptance matrices are used to calculate the mobility matrices of the modified structure. The mobility matrices are then used to calculate the velocities at the structural nodes under the effect of the excitation forces. The calculated velocities are used as boundary conditions for the acoustic analysis to calculate the nodal pressures at the predefined locations.

Subject Keywords

Vibro-acoustic analysis, Structural modification, Vehicle interior noise

URI

https://hdl.handle.net/11511/105211

Collections

Department of Mechanical Engineering, Conference / Seminar