A broadband sound absorption resonator made of acoustic black hole

In this paper, an acoustic resonator designed for broadband sound absorption is proposed. The resonator features a neck that extends into the cavity, forming a sonic black hole. This design incorporates a central pore profile that decreases linearly across a series of interconnected annular cavities. The radii of the necks connecting these cavities progressively decrease from the inlet, while the resonator's wall is considered rigid. The finite element method is used to calculate both the sound absorption coefficient and the surface impedance of the proposed resonator. When the neck comprises fifteen annular cavities, the sound absorption coefficient exhibits fifteen different resonant peaks. By reducing the thickness of each annular cavity to approximately 1 millimeter, a broadband sound absorption coefficient is achieved with a surface impedance closely matching that of air. The proposed resonator demonstrates very good performance in noise attenuation across a wide frequency range, making it a promising solution for effective noise insulation in various applications.