Vibroacoustic metamaterials in sheet metal structures for the reduction of sound radiation

Vibroacoustic Metamaterials (VAMM) are composed of periodically arranged unit cells, each consisting of a section of the base structure and a resonator. The virtual negative stiffnesses or masses resulting from the local resonance effect create a stop band in which no free wave propagation is possible. This stop band can be tuned in terms of its bandwidth, amplitude reduction, and position in the frequency range by adjusting the properties of the resonators. Metamaterials are often manufactured using 3D printing processes. However, for the production of large quantities, other manufacturing methods are required. Stamping, laser cutting, or waterjet cutting are common mass-production-compatible processes for producing sheet structures and are also suitable for manufacturing VAMM. Therefore, this contribution presents various unit cell designs that can be manufactured using the aforementioned processes and describes their advantages and disadvantages. For example, some designs allow the integration of multiple resonances into a single unit cell within the relevant frequency range, leading to multiple or wider stop bands. The potential of sheet-based VAMM is demonstrated on a grinding machine stand, an inverter cover of an electric drive, and a sound-absorbing noise barrier and a saw blade. Vibration reductions of up to 20 dB are achieved.