A comprehensive model to predict acoustic absorption factor of porous mixes

The aim of this study is to define an experimental model to predict acoustic absorption properties of porous asphalt concretes (PAC) as a function of composition and volumetric characteristics of mixes. The model can be used for the mix design of PAC and it enables to individuate which composition parameters to operate on in order to obtain optimum acoustic performances of low noise porous pavements. In order to define the experimental model, a large number of asphalt concrete samples, with high void content and composed of both different aggregate grading and different bitumen percentages were compacted in laboratory. Noise absorption spectra were determined on these samples by means of the stationary wave impedance tube. The measured amplitudes of the acoustic absorption spectrum were fitted by the Neithalath microstructural model in order to determine, for each sample, the pore geometry which allows to reproduce the measured acoustic absorption spectrum. After that, the pore geometry was related to composition and volumetric characteristics of mixes by means of multivariate regression techniques. By this way, the acoustic absorption spectrum of PAC can be predicted as function of specific composition parameters.