Acoustic performance evaluation of a panel utilizing negative stiffness mounting for low frequency noise control

Abstract

In order to encounter the challenges of low frequency noise absorption below 100 Hz, primarily emitted from the engines in air and ground vehicles, a method of acoustic panel mounting is proposed based on the KDamper concept which utilizes the negative stiffness damping effect. The practical constraints in such applications relating to the thickness of the panel for adequate noise absorption, are compensated through the unique damping properties of the KDamper and the ability to attenuate low frequency excitation in a considerable range. Therefore, a preliminary implementation of an acoustic panel with appropriately designed elastic mounts incorporating negative stiffness elements, is evaluated in terms of acoustic performance. During the design stage of the mounting, the problem is approached as in the case of classic vibration isolation of a rigid mass, due to the nature of the low frequency excitation. However, the elasticity of the deformable thin plate is taken into account by modeling its dynamic behavior using generalized modal values. The investigation consists in establishing the theoretical framework of the problem for the examination of metrics such as the sound transmission loss (STL) and the optimization of the mounting in order to maximize the STL performance, accompanied by FEM simulations. Additionally, comparisons with conventionally mounted panels is provided for reference and to highlight the advantages of the proposed solution. Early results regarding the noise control capabilities of such a panel configuration, indicate the potential of this proposition in specific applications.