IMPROVEMENT OF LOW-FREQUENCY SOUND ABSORPTION PERFORMANCE BASED ON THE GRADUAL HELICALLY PERFORATED POROUS MATERIALS

The traditional acoustic packaging is difficult to achieve the low-frequency sound absorption performance below 500 Hz, and the double porosity structure has the potential to improve the poor low-frequency sound absorption performance. In order to achieve excellent subwavelength sound absorption performance, a kind of helically perforated porous metamaterial with gradual dimensions is designed in this paper. The theoretical model of sound absorption is established by means of equivalent medium and transfer matrix method. Through finite element method, the accuracy of the theoretical model is verified. It is evident that the metamaterial can achieve a perfect impedance match with air at low frequency, because the helical perforation makes the air more easily enter the porous material and promotes the particle resonance and sound energy dissipation. The parametric discussion and analysis show that different dimensions will change the peak frequency and bandwidth range of sound absorption. In order to achieve the excellent sound absorption performance of both low frequency and wide band, the parallel and series gradual helically perforated metamaterial are proposed. The artificial bee colony algorithm is used to further optimize the size parameters and achieve excellent sound absorption performance in the low frequency range of vehicle noise. This paper can provide reference for the design of automotive acoustic packaging which can suppress low frequency noise.