Advanced negative stiffness absorber for low-frequency noise insulation of panels

Abstract

The sound transmission loss of conventional means of passive acoustic treatment in the low-frequency range is governed by two physical mechanisms: the inertia, as stated by the mass density law, and the local resonances of the structure. Since usual partitions are flexible and lightweight, their acoustic performance is poor, especially below 300 Hz. Although conventional acoustic meta-materials can offer excellent acoustic properties, they also perform poorly in this range. Therefore, novel meta-structures are required to overcome these limitations. This proposed novel absorber optimally combines the concepts of KDamper (KD) and inertial amplification mechanisms (IAMs). The novelty of the KD-IAM absorber lies in the generation of equally deep but significantly wider attenuation bands surpassing the mass density law while requiring only a small fraction of additional mass. The absorber is implemented and demonstrated as an elastic mount for retrofitting existing panels, essentially manipulating the resonant response of the structure by controlling the panel’s boundary conditions. It is also shown that increasing the panel’s rigidity and, consequently, its fundamental eigenfrequency utilizing stiffeners results in further improvements in the bandwidth and depth of noise attenuation. A wide and deep attenuation band is demonstrated in the resonance region below 120 Hz, up to 13 dB above the reference level. An indicative design and implementation for a case study are presented. It is further demonstrated that the same concept can be utilized for the formation of meta-structures by periodic repetition of KD-IAM unit cells, leading to significant additional attenuation of the lowest vibration modes.

Collaborative Design of Static and Vibration Properties of a Novel Re-Entrant Honeycomb Metamaterial

“…Among them, the local resonance effect can promote the generation of a low-frequency bandgap, which can be explained by the mass-spring physics principle. In this principle, the metamaterial structure is equivalent to a "mass-spring" system, in which the natural frequencies of each order and the upper and lower bounds of the bandgap are determined by the equivalent mass and equivalent stiffness [39]. Mukherjee et al [40] designed a new honeycomb lattice metamaterial by combining the traditional and additive material lattices, and its bandgap performed better than the traditional honeycomb metamaterial in the low-frequency region.…”

3d Numerical Investigation of an Extended Kdamper Absorber for Seismic Retrofitting of Low-Rise Buildings

“…The stiffness-mass elements can be allocated appropriately to create a system that is statically and dynamically stable, maintaining the structure's initial/static stiffness and avoiding potential instabilities. The KDamper has been examined in protecting bridges, wind turbines, and other structural systems, resulting in reduced displacement demand at the base level [12][13][14][15][16].…”

A negative stiffness dynamic base absorber for seismic retrofitting of residential buildings

“…The system combines the beneficial characteristics of the NS and of the traditional TMD, leading to a device that introduces extraordinary damping properties to the structure. By incorporating the additional NS element, the inertial forces of the damper are increased, and the need for large mass is significantly reduced 27–29 . In addition, the proper allocation of the stiffness–mass elements of the device leads to a system that is both statically and dynamically stable; the properties of the KDamper can be designed in order to maintain the initial/static stiffness of the structure and, hence, avoid potential instabilities.…”

“…By incorporating the additional NS element, the inertial forces of the damper are increased, and the need for large mass is significantly reduced. [27][28][29] In addition, the proper allocation of the stiffness-mass elements of the device leads to a system that is both statically and dynamically stable; the properties of the KDamper can be designed in order to maintain the initial/static stiffness of the structure and, hence, avoid potential instabilities. This vibration control system has been examined for the protection of bridges 30,31 wind turbines, 32,33 and structural systems, [34][35][36] achieving reduction of the displacement demand at the base level.…”