Metamaterials are man-made materials which behaves in a unique way and possesses exclusively desired properties that are not found in natural materials. Usually, it is the combination of two or more materials and can be engineered to perform tasks that are not possible with traditional materials. These were initially discovered while working with electromagnetic radiation.  Apart from electromagnetic radiation, metamaterials are also capable of affecting the wave propagation characteristics through any fluid such as air. These metamaterials are called acoustic metamaterials. Many acoustic metamaterials have gone beyond its definition but still characterize the wave guiding properties. Incorporation of smart materials while constructing acoustic metamaterial, can lead to achieving multifunctionality of the design. A prospective application field for such acoustic metamaterials is energy harvesting from low frequency vibrations. Conventionally, acoustic metamaterials are used as noise barrier materials to filter roadside and industrial noise. This application can get extended to aerospace application where engine noise mitigation inside the cabin is a challenge these days. In this article, a spiral shaped acoustic metamaterial is modeled which has dual function of noise filtering and energy harvesting. This acoustic metamaterial has comparatively high reflection coefficient closer to the anti-resonance frequencies, resulting in high sound transmission loss. The filtered noise is trapped inside the cell in the form of strain energy. Hence, we claim that if the trapped energy which is any way wasted in the material could be harvested to power the local electronic devices, the new solution could make transformative for 21st century’s green energy solution. Calculated placement of smart materials in the cell matrix can help extracting the strain energy in the form of power. The acoustic metamaterial cell presented in this work has the capability of isolating noise and reducing diffraction by trapping sound in low frequencies and at the same time recover the trapped abundant energy in the form of electrical potential using piezoelectric materials.  The spiral design is sensitive to vibration due to cantilever shaped attachments inside the cell. This makes it capable of harvesting energy using vibration also. This is a promising acoustoelastic metamaterial with multifunctionality properties for future applications.


Performance of a Multifunctional Spiral Shaped Acoustic Metamaterial With Synchronized Low-Frequency Noise Filtering and Energy Harvesting Capability

Division / Sponsors: 
Aerospace Division

Paper Proceedings: https://asmedigitalcollection.asme.org/SMASIS/SMASIS2020/volume/84027

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