Acoustic metaliners for insulating noise in a duct with varying cross-sectional area

Abstract

We propose a sound-insulating acoustic metaliner for a duct with varying cross-sectional area with consideration of the flow that varies along the direction of flow and is not a fully-developed. The metaliner comprises an array of unit cells based on two different types of Helmholtz resonators and installed on the duct wall to preserve ventilation performance. To consider the effect of flow on the sound insulation performance of the metaliner, we establish an effective impedance model in term of the friction velocity, enabling the consideration for flows that are not fully-developed. The geometrical parameters of unit cells of the metaliner are designed individually considering the flow around each unit cell. The sound insulation performance of the designed metaliners for different flow speeds with the target frequency of 900 Hz is verified experimentally.