Multifunctional hybrid metastructure with a combination of flower-shaped Helmholtz resonator and spiral labyrinth: Synergy enhancement in broadband sound absorption and high energy absorption performance

Abstract

The increase of the running speed of high-speed trains is accompanied by the continuous increase of the internal noise of the carriage, and the total noise reduction capacity of the sandwich structure, which is the main component of the carriage wall, is limited under the constraints of space dimension and size, which poses a new challenge to the acoustic performance design of the sandwich structure. Based on that, this paper proposes a novel compact composite structure, which consists of a flower-shaped Helmholtz resonator incorporating an embedded tube, a microperforated plate, and a spiral-shaped labyrinth sound-absorbing structure from top to bottom. Simulations of the structure were performed utilizing the finite element analysis software COMSOL, and the results were verified through standing wave tube sound absorption tests. A strong alignment was noted between the experimental outcomes and the simulation results. The results reveal that the average sound absorption coefficient of the structure surpasses 0.95 within the frequency band of 394 Hz to 548 Hz, achieving nearly perfect sound wave absorption. At the resonance frequency of 394 Hz, the peak absorption coefficient attains 0.981369, despite the structure’s thickness being only one-fifteenth of the wavelength corresponding to the absorption peak frequency, highlighting its distinctive deep-subwavelength properties. Even when the structure’s height is reduced to 60 mm, it maintains a wide sound absorption bandwidth, featuring a bandwidth ratio of 70 % where the sound absorption coefficient exceeds 0.5. The structure exemplifies deep-subwavelength properties by effectively managing large wavelengths despite its small size. Furthermore, the energy absorption characteristics of the composite structure are analyzed. It is found that the composite structure has excellent energy absorption characteristics and sound absorption performance. This study proposes a lightweight metastructure with exceptional acoustic performance, it has potential application value in the skin structure of high-speed trains and other transportation equipment.