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Extreme material parameters accessible by active acoustic metamaterials with Willis coupling
Steven R Craig1, Bohan Wang1, Xiaoshi Su2
1George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332, USA.
The Journal of the Acoustical Society of America
|April 2, 2022
Summary
This study introduces an active acoustic metamaterial with Willis coupling, significantly expanding the tunability of effective material properties. This breakthrough broadens applications in acoustics, imaging, and cloaking.
Area of Science:
- Acoustics and Materials Science
- Metamaterials Engineering
Background:
- Active acoustic metamaterials use electric circuits to tune material properties.
- Conventional designs lack tunability due to unconsidered Willis coupling.
Purpose of the Study:
- To propose an active acoustic metamaterial incorporating Willis coupling.
- To significantly extend the tunability of effective density and bulk modulus.
Main Methods:
- Designed a unit cell with two sensor-transducer pairs for asymmetric signal feedback.
- Implemented feedback control circuits with unequal gains to induce Willis coupling.
Main Results:
- Achieved a two-orders-of-magnitude increase in the accessible parameter range for effective density and bulk modulus.
- Demonstrated extended tunability compared to non-Willis metamaterials.
Conclusions:
- The proposed active metamaterial with Willis coupling offers unprecedented tunability.
- Expanded parameter range enables advanced applications in biomedical imaging, noise control, and cloaking.
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