Broadband characteristics and bandpass acoustic focusing via movable second-order Helmoltz resonator

In this paper, a method is theoretically proposed to obtain a novel movable second-order Helmholtz resonator by adding a perforated plate inside the cavity of the Helmholtz resonator that can be freely tuned up and down. Through software simulation, it is concluded that the resonator meets the design objective of saving production costs that when the manufactured physical object is required to change the structural parameters, it only needs to be dynamically adjusted on this basis, rather than needing to reproduce a new physical object with new structural parameters. Meanwhile, it has excellent acoustic characteristics, with a stop band in the range of 80-610Hz at the low frequency and a bandpass acoustic focusing characteristic in the range of 4050-5250Hz. It can achieve directional adjustable focus acoustic focusing for plane waves incident at any angle, and directional adjustable focus acoustic focusing for cylindrical wave incidence, with excellent focusing effect. The added perforated plate changes the resonator one-item structure model and can be reused to meet different structural parameters.