Scientific Article

Noise mitigation with active acoustic metamaterials

¹ Department of Mechanical Engineering, University of Michigan, Ann Arbor, Michigan 48109, USA
² Department of Electrical Engineering and Computer Science, University of Michigan, Ann Arbor, Michigan 48109, USA
³ Toyota Research Institute of North America, Ann Arbor, Michigan 48105, USA

^* Corresponding author: This email address is being protected from spambots. You need JavaScript enabled to view it.

Received: 31 December 2025
Accepted: 7 April 2026

Abstract

The potential of active metamaterials to address long-standing challenges such as noise mitigation has been recognized for several decades. However, the research of active structures capable to meet these challenges has been slow due to issues such as stability and limited bandwidth. This work will feature a class of active metamaterials composed of independent unit cells with sensors and actuators connected through electronics that impose desired transfer functions between these elements. We experimentally demonstrate two implementations of these active metamaterials for the application of noise mitigation. In the first case, a two-dimensional metamaterial is digitally programmed to behave with complex effective bulk modulus and mass density that have matched phases. With these properties, the metamaterial achieves very high sound absorption, but is well-matched to the background and thus scatters very little. Moreover, its acoustic behavior can be switched from opaque absorber to transparent medium on very small time scales. In the second case, broadband noise absorption in a duct is targeted through the design of a one-dimensional active metamaterial with analog circuitry. The transmission loss can be increased by adding cells to the metamaterial while maintaining stable performance.