This experimental project is being conducted as a part of WSDOT’s effort to produce pavements that reduce the noise generated at the tire/pavement interface. Experimental sections of open-graded friction courses (OGFC) were built using asphalt rubber (AR) and styrene-butadiene-styrene (SBS) polymer modified asphalt binders. A section of conventional Class ½ inch hot mix asphalt (HMA) serves as the control section for the two experimental sections.
Sound intensity measurements were conducted using the On Board Sound Intensity (OBSI) method immediately after construction and monthly, weather permitting, for a year following construction.
OBSI readings immediately after construction indicated that the OGFC-AR and OGFC-SBS sections were 2.8 to 3.8 decibels, respectively, quieter than the Class ½ inch HMA control section. Data from one year later showed that the AR and SBS modified sections were 1.5 to 3.3 decibels quieter, respectively, than the control section. Sound intensity readings taken between wheel paths are at levels similar to the initial readings after the sections were constructed indicating that studded tire wear is having a negative effect on the sound absorbing qualities of the open-graded mixes.