An acoustic metasurface for noise mitigation
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Periodicity in media is exhibited either through its geometry or boundary conditions. Metamaterials are engineered structures that exploit such periodicity to achieve tailored properties for vibration and noise mitigation [1]. Classically, resonant bandgaps are implemented for targeting low frequency noise mitigation as they do not depend of the unit cell length. However, passive linear metamaterials do not offer smart and adaptive behaviors, while achieving only narrow frequency bandwidths of efficiency for resonant bandgaps. Meanwhile, nonlinear responses feature many phenomena extremely useful for noise mitigation such as the Targeted Energy Transfer. Among them, nonlinear responses can increase the resonant bandgap’s bandwidth, in addition to energy scattering towards higher harmonics, which would considerably improve noise mitigation. In Acoustics, nonlinear responses are usually activated above a high excitation amplitude threshold, leading to recent studies for developing electroacoustic nonlinear resonators operating at low excitation amplitudes by active control [2]. Consequently, this work focuses on the development of a digitally programmable nonlinear metasurface at low excitation amplitudes. In this contribution, we study an acoustic liner made of independent electroacoustic resonators featuring nonlinear behavior thanks to a digital controller [3, 4]. The global response and performance of the system is experimentally assessed though the 4-Microphones Method and compared against Finite Element simulations.
