Ultra-broadband acoustic metaliner for fan noise reduction

Abstract

Fan noise, characterized by its broadband nature and spatial constraints, poses a significant challenge in noise control . Traditional acoustic liners, typically local, do not sufficiently address resonance mode coupling , rendering them inadequate for modern engineering requirements. Moreover, anti-resonance effects among these modes further weaken their broadband noise attenuation capability. By contrast, nonlocal metasurface liners employ global resonance modulation, allowing precise control of resonance mode coupling for improved noise attenuation. In this paper, we introduce an ultrathin nonlocal acoustic metaliner, designed via a mode matching method, which offers global resonance modulation and effectively suppresses anti-resonance between resonance modes, thereby mitigating broadband fan noise. Operating between 1000–5000 Hz , the metaliner achieves a deep sub-wavelength thickness of just 20 mm ( ∼ λ / 17 ). Fan tests indicate a 2.4 dB reduction in total sound pressure levels in all directions. This approach highlights the practical applications of acoustic metamaterials , broadening their utility and enhancing noise control engineering.