Research on the Sound Absorption Performance of Porous Asphalt Concrete with Different Air Voids Based on the Finite Element Models

This paper aims to investigate the effect of the void structure of porous asphalt concrete (PAC) on the sound absorption performance. The sound absorption coefficient (SAC) spectra of PAC with various voids were measured using the transfer function method and the air void structure was identified from Computed Tomography (CT) scanning images. The finite element model (FEM) of the void structure was established via CT cross-sectional images to research the noise reduction mechanism of PAC. At different frequencies, the sound pressure level distribution and SAC were calculated. The following are the main conclusions: (1) As the void content of PAC increases, the SAC spectrum curve becomes higher, more rightward and wider, while the peak values, their corresponding frequencies and mean values increase. (2) The SAC decreases with the average number of voids within each image and increases with the void equivalent diameter and fractal dimension; there exist linear relationships between these three parameters and the SAC. (3) The sound absorption capacity of the void with larger size and fractal dimension is higher than the smaller one and the voids connected to the upper and lower surfaces provide more noise reduction. (4) The FEMs of PAC can predict the SAC of PAC