Vibroacoustic metamaterials for influencing vibroacoustics by means of resonator effect

passive vibration reduction measures, structural dynamics

The »MetaVib« project involves researching vibroacoustic metamaterials and developing these as an innovative vibration reduction measure. They are suitable for application in a wide range of industries, e.g. mechanical engineering, the automotive sector or aerospace. At Fraunhofer LBF, work is being carried out in the areas of conceptual design, numerical and experimental characterization to close the research gap in systematic design processes.

How do vibroacoustic metamaterials work?

Research into vibroacoustic metamaterials is currently being carried out across the world. With their help, the amplitudes of harmful structural vibrations and noise can be reduced to a depth and broadband that is practically impossible to achieve using conventional measures. These metamaterials are made of periodically arranged passive or active local resonators applied to the component that is to be influenced. The local resonators are tuned to the addressed resonant frequency and placed on the basic structure at intervals smaller than half the wavelength of the frequency to be influenced. In this frequency range, so-called “stopbands” – areas in which no wave propagation is possible – are then created in the transfer function.

Virtual development process for specific applications

Currently, the design and manufacturing of vibroacoustic metamaterials is mostly done without a sufficiently systematic approach or consideration of economical manufacturing processes. These issues are addressed in the internal Fraunhofer PREPARE project »MetaVib«. The cross-institutional research teams develop the design, simulation and manufacturing of passive and active vibroacoustic metamaterials. The methodology developed is validated using two application-oriented demonstrators: A vehicle door is used for structure-borne noise reduction and on a silencer is used for influencing acoustics. Furthermore, in the case of acoustics, active vibroacoustic metamaterial concepts are considered and prototypically implemented.

At Fraunhofer LBF, the focus is on an application-oriented virtual development process, which includes the development of concepts and their numerical preliminary designs. The design process is independent of the application, and, in »MetaVib« its effectiveness is demonstrated on a vehicle door. Concepts involving vibroacoustic metamaterials for defined frequency ranges consisting of metal or plastic taken into consideration. The concepts are designed in detail using numerical routines. The knowledge gained is implemented in the form of a toolbox that enables the design and optimization of structures as vibroacoustic metamaterials at different levels of detail.

Funding: Fraunhofer »PREPARE« internal program, partner institutes: Fraunhofer IBP, Fraunhofer IDMT, Fraunhofer IFAM, Fraunhofer IWU