Extended tube acoustic metamaterial: Its modeling and application to a kitchen hood.

In this work, acoustic metamaterials based on the concept of extended tube are investigated. The metastructure consists of an array of units, each featuring a thin tube protruding from a perforation into a backing cavity to form a Helmholtz resonator. First, an impedance model for a single-layer extended tube structure is developed using the equivalent circuit method. For the tube in which the viscothermal effect can not be ignored, an equivalent fluid model is used to characterize its acoustic property and end corrections are introduced to take into account the flow distortion effect at the two ends. Then, two cost-effective samples are fabricated and tested using the impedance tube where good accuracy between the prediction and measurement is found. The structural simplicity and low-frequency absorption property allow the extended tube acoustic metamaterials to be utilized in scenarios where installation space for acoustic absorption materials is constrained. As an example, we demonstrate its use on a commercial kitchen hood. Standard acoustic power measurement shows its superior noise reduction performance over conventional porous materials of the same thickness. [ABSTRACT FROM AUTHOR]