Principal Components Regression of Onboard Sound Intensity Levels

Roadways paved with open graded asphalt mixes typically generate lower traffic noise levels as compared to other types of pavements. A program was initiated in 2005 in California to evaluate the effectiveness of noise reducing surfaces over time and the pavement characteristics affecting those noise levels. In this study, tire/pavement noise was measured using the onboard sound intensity method. Data were collected on four different types of mixes: conventional open graded asphalt concrete, rubberized asphalt concrete that are open graded, rubberized asphalt concrete that are gap graded, and dense graded asphalt concrete mixes. A total of 72 field pavement sections that were at that time less than 8years old were included in the study. Various pavement characteristics were measured and their effects on noise levels were evaluated using principal components regression, in addition to ordinary least-squares regression. This research confirmed that open graded pavements exhibit reduced tire noise compared to dense and gap graded mixes and quantified this reduction for typical mixes in California.