Low frequency and broadband sound attenuation by meta-liner under grazing flow and high sound intensity

Acoustic liners are the most effective solution to attenuate the noise of ducts with flows but still suffer from narrow sound absorption bandwidth and heavy bulk. In this work, we present a new type of acoustic meta-liner structure, which is composed of perforated plates and coiled-up Fabry-Perot (FP) channels with carefully designed equivalent length. By tuning the geometric parameters of the perforated plate and the optimal combination of the coiled-up FP channels, perfect impedance matching is achieved in a broadband range. The strong dissipation of sound energy could also be observed under different speeds of grazing flow and high incident sound intensity. It is analytically, numerically, and experimentally demonstrated that for the structure, over 90% sound absorption is achieved in the broadband range from 500 to 3000 Hz in the absence of flow and the condition of grazing flow with a speed of 30-98 m/s, coupled with a 90-130 dB incident sound pressure level. Moreover, the thickness of the proposed simply structured meta-liner is 44 mm, which is only 8/125th of the wavelength corresponding to 500 Hz. As a deep sub-wavelength liner, it exhibits potential application prospects in the field of fluid-solid coupled machinery such as aero-engine systems and ventilation duct systems. (C) 2022 Author(s).

Automated summary

This paper presents a new type of acoustic meta-liner structure that achieves perfect impedance matching and efficient sound energy dissipation in a broadband range. Experimental and numerical results demonstrate over 90% sound absorption in various conditions.