Numerical and Experimental Results of Passive Control for Noise and Vibration Reduction

During last years many research projects have been funded by European and American Institutions with the aim to increase passengers ’ acoustical and vibrational comfort, in aerospace as well as in automotive field. In order to control noise radiated and vibration levels in vehicles and structures, different approaches have been used. Hybrid active-passive damping treatments seem to be the most effective by combining robustness and reliability of passive methods with high performance of active ones. Experiences gained on using passive damping treatments, mainly on 2-D structures, have been used for studying typical truss space structures and assessing the ability of damping treatments to reduce structural vibrations. In addition, the temperature sensitivity of viscoelastic damping materials has been experimentally measured and its effect simulated in numerical models. The paper presents the characteristics of viscoelastic damping materials within “glassy ” and “rubbery ” behaviour’s typical temperature, and discusses the possibility to use them, in a numerical model, for simulating damping treatment’s effect in operating conditions on dynamic response of a truss structure. The results obtained during these preliminary studies are quite discouraging leading to the conclusion of the inefficient use of such damping treatments for truss-like structures. Completely different results are obtained, on the other hand, when using active control approach, which may be even technologically more efficient, for such kind of structures. As a final results a sort of hybrid truss-panel structure has been studied which may offer an alternative approach to reduce the vibrations of such typical structural architecture