Broadband sound attenuation by metaliner under grazing flow
Sibo Huang, Enmin Zhou, Zhilong Huang, Pengfei Lei, Zhiling Zhou, Yong Li
Abstract
Acoustic liners are the most effective passive solution to noise emission from ducts but still suffer from the drawbacks of narrow-band performances and thick structures for the conventional designs. Here, we present an acoustic metaliner capable of high-efficiency broadband sound attenuation under grazing flow. The metaliner is composed of a perforated plate and a metasurface consisting of a series of neck-embedded Helmholtz resonators (NEHRs). By tuning the nonlocal coupling among the NEHRs and the perforated plate, efficient broadband impedance modulation can be realized, leading to a strong dissipation of broadband sound energy under various speeds of grazing flow. We theoretically and experimentally investigate a well designed metaliner, which can strongly attenuate sound energy for a wide frequency range from 800 Hz to 3000 Hz, both in the absence of air flow and in the presence of grazing flows with speeds from 10 m/s to 60 m/s. Besides, the thickness of the metaliner is only 40.5 mm. Our work provides a route to reduce flow-related noise in a broad frequency range and may find applications in airplane propulsion systems, air-conditioning systems, and other mechanical systems with flow.