Empirical acoustic model for asphalt surface mixes

In this paper, an empirical acoustic model was developed for four asphalt surface mixes, including conventional dense-graded asphalt concrete (DGAC), open-graded asphalt concrete (OGAC), rubberized open-graded asphalt concrete (RAC-O), and rubberized gap-graded asphalt concrete (RAC-G). Tire/pavement noise data were collected and converted from in-service flexible pavements using an on-board sound intensity (OBSI) method, for four consecutive years. Because the panel structured noise data contain potential violations to basic assumptions of ordinary least square models, several econometric techniques were used to address the violations and develop rational models. Specifically instrumental variables and a multinomial logit (MNL) model were used to address endogeneity and a two-way random-effect model was used to capture the unobserved heterogeneity. Te estimated model suggests that tire/pavement noise increases with pavement age and mean profile depth (MPD), and decreases with air-void content of surface mixes. The noise levels of the four asphalt surface mixes rank as: RAC-O < OGAC < RAC-G < DGAC.