Add-on damping patches efficiency on sound transmission of a thin plate under aerodynamic or acoustic excitation

摘要

The turbulent boundary layer excitation is one of the main sources of aircraft interior noise over a large frequency range while the diffuse sound field excitation is often considered as an approximation for noise analysis and noise control evaluation. In this context local damping effect is investigated through the use of add-on damping patches in comparing insertion losses through a thin plate under both excitations. A thin plate having its critical frequency equal to 4400 Hz and its aerodynamic coincidence frequency equal to 1100 Hz is considered. Numerical results are carried out using an original methodology based on the Minimization of Error on a Sample of Observation Points (MESOP). The transmission loss index is assessed in the frequency range 50 to 7000 Hz. This investigation points out different behaviors: a damping effect is observed only in the critical frequency region under diffuse sound field excitation whereas the transmission loss index is increased over the whole frequency band under turbulent boundary layer excitation. The transmission loss under aerodynamic excitation with varying patch sizes is finally investigated in the context of damping treatments optimization.