Spiral Acoustic Metamaterial Coupling Local Resonance and Bragg Scattering for Ducted Fan Noise Mitigation

Abstract Acoustic metamaterials based on the principle of localized resonance tend to have a narrow absorption band, which limits their potential application for fan noise control. To address this challenge, a spiral acoustic metamaterial is developed that combines the local resonance mechanism with the Bragg scattering mechanism. This design not only effectively broadens the absorption bandwidth at the target frequency and achieves broadband absorption centered on multiple harmonic frequencies, but also compensates for the size‐related limitations associated with the Bragg scattering mechanism. The theoretical model of the acoustic metamaterial, based on the coupling mechanism, is developed using the transfer matrix method. The bandgap analysis demonstrates that the acoustic absorption bandwidth increases by ≈50% following the coupling process. Simultaneously, the design of the spiral structure results in an overall size reduction of ≈67% compared to conventional periodic metamaterials. It is verified through numerical simulations that the designed metamaterial exhibits efficient ventilation capabilities, but the ventilation efficiency decreases with the increase of the number of periodic units. Samples are fabricated for experimental validation via 3D printing technology, and the experimental results demonstrated that the designed acoustic metamaterials are effective in attenuating fan noise.